Attack pattern

Persistent Prompt Injection

How prompt injection influence survives the initial encounter through retained state or repeatedly reprocessed sources, and why a memory write, a later retrieval and an unauthorized action are three different security facts.

By Norbert HofmannPublished: 2026-09-20Last reviewed: 2026-09-20Level: AdvancedAudience: Security Engineers, Developers, AI Engineers
Entry paths
Direct and indirect
Distinctive property
Influence survives the initial encounter
Level
Advanced
Closest OWASP class
LLM01:2026, ASI06 (2026)
Table of contents

What Is Persistent Prompt Injection?

Persistent prompt injection describes prompt-injection influence that outlives the encounter in which it entered. The content that carried the influence is either written into state the system keeps, or it remains reachable at a source the system reads again, so a later task, a later session, another user or another agent can be affected by material nobody supplied in that later moment.

The entry mechanism is not new. Competing instructions still arrive through an intended input channel, as described under direct prompt injection, or through external content the system retrieves, reads or processes, as described under indirect prompt injection. What this article is about is the lifecycle afterwards: what the system retains, whether and how the provenance of that retained material is preserved, weakened or lost, when it becomes model-visible again, and which decisions stand between reactivation and an actual security effect.

Persistence Is a Lifecycle Property, Not a Third Entry Mode

It is tempting to file persistence next to direct and indirect as if it were a third way in. It is not. Every persistent case begins as one of the two established entry modes and then acquires a second property: the influencing material, or a derivative of it, survives.

What changes when influence persists
AspectSingle encounterPersistent case
EntryDirect or indirectDirect or indirect, unchanged
Survival beyond the initial encounterInfluenced state or source does not persist past the encounterInfluenced state or a reachable source survives and can re-enter later contexts
Number of context assemblies affectedContexts reached during the current encounterCan recur in later contexts or sessions
Provenance riskProvenance can be weakened or lost during transformations in the current encounterProvenance can be weakened or lost across writes, later retrievals and transformations over time
Affected principalsThe current user or taskLater tasks, other users or other agents, only if retrieval boundaries permit
RemediationNo persistence cleanup once the context or source no longer re-enters, though executed side effects still need normal remediationSecure or remove the persistent source, locate and invalidate derivatives that actually exist, and remediate any executed effects

Reading persistence as a property rather than as a class keeps two useful questions separate. First, how did the content enter? Second, what did the system decide to keep, and under which authorization? The second question is where the specific controls of this article live.

Scope and Neighbouring Classes

Related classes and how they differ
ClassDefining mechanismRelationship to this topic
Memory and Context Poisoning (ASI06:2026)Stored or retrievable context is corrupted or seeded with misleading dataThe closest current agentic classification for the derived-state family
Prompt Injection (LLM01:2026)Inputs alter model behaviourThe entry mechanism; one-time prompts stay here
RAG prompt injectionRetrieved passages carry instructions into contextA retrieval path that can produce persistence, but is not identical with it
Data poisoningTraining or fine-tuning data is manipulatedDifferent lifecycle stage: affects the model, not the runtime state
Model poisoningModel weights or artifacts are manipulatedA supply-chain compromise of the model itself
Configuration compromiseDeterministic settings, hooks or instruction files are alteredMay be a system compromise in its own right even when the visible effect is persistent model influence
Cascading failuresOne faulty component drives further failuresA possible consequence pattern, not the definition

Two Families of Persistence

Persistent prompt injection is broader than memory poisoning, because a system can be repeatedly influenced by the same material without ever writing a memory object. Two families deserve equal treatment.

01
FamilyRetained derived or internal state

Long-term memory entries, conversation summaries, compaction artifacts, user preferences and profile state, scratchpads, workflow notes, caches, embeddings and index entries, shared agent memory, and local configuration or hook-like state that is later injected into context.

02
FamilyRepeatedly reprocessed external source state

Attacker-reachable repository files, tickets, wiki pages, documents, mailboxes or web resources that stay in place and are re-read whenever a similar task runs. No write into the application is needed for the influence to recur.

The two families fail differently. Derived state can be less visible and harder to audit for the person affected, and it carries an implicit claim of relevance. Reprocessed sources may be visible depending on the system and workflow, but they keep producing influence until someone changes the source or the retrieval policy. A programme that only hardens memory writes will keep re-reading the poisoned file; a programme that only cleans sources will keep the summary that condensed it. Both are addressed under source code prompt injection and RAG prompt injection from the vector side; here they are treated as persistence surfaces.

The Persistence Lifecycle

From controlled source to security-relevant effect
UntrustedAttacker-controlled source or input
UntrustedContent becomes model-visible
Variable trustRetained source or written derived state
Variable trustProvenance, scope or TTL weakened
SystemRetrieval / Context Selection
Variable trustRe-exposed Stored Content
Variable trustReactivated model influence
SystemReachable data or capability path
SystemExternal authorization decision
Variable trustObserved effect

Every arrow in that chain is a place where the attempt can end. Content can be model-visible without ever being retained. It can be retained without being retrieved again. It can be retrieved and summarised into something that no longer carries the instruction. It can reactivate influence and still produce nothing but a rejected proposal, because the authorization layer does not consult the model about what it is allowed to do.

Security States That Must Be Kept Apart

Distinct states with distinct evidence
StateWhat it establishesWhat it does not establish
Placement or writeControlled content entered a persistent surfaceThat anything will ever read it again
Later retrievalThe stored item was selected into a later contextThat the model was influenced by it
Re-exposureThe item became model-visible again in its stored formThat behaviour changed
Model influenceOutput, plan or tool choice measurably changedThat a policy was bypassed
Policy bypassA control that should have stopped the step did notThat an action was executed
Unauthorized actionAn action outside the authorized scope took effectThe extent of the damage
Security impactA concrete effect on confidentiality, integrity or availabilityNothing further is assumed

The same discipline applies to the word compromise. A written memory entry containing influenced text is a security-relevant state change and deserves an investigation. It is not, by itself, a compromised system, a compromised user account or a compromised model.

Persistence Surfaces Inventory

01
SurfaceMemory store CRUD

Explicit remember, update and delete operations, whether model-proposed or user-initiated.

02
SurfaceSummaries and compaction

Condensed history that replaces the original turns once a window fills.

03
SurfaceEmbeddings and indexes

Vector entries derived from influenced text that remain retrievable after the source changes.

04
SurfaceCaches and grounding stores

Cached answers, fetched pages and grounding snapshots reused for later similar requests.

05
SurfaceConversation history

Retained transcripts replayed into later sessions or shared across devices.

06
SurfacePreferences and profile state

Stored rules about how the system should behave for this user or project.

07
SurfaceTask and workflow records

Notes, plans, tickets and scratchpads that later runs read as working context.

08
SurfaceShared agent memory

Blackboards and shared stores several agents write to and read from.

09
SurfaceRepository instruction and configuration files

In-repo instruction files and hook-like configuration that are loaded into context on later runs.

10
SurfaceRepeatedly reprocessed artifacts

Documents, pages and tickets that stay in place and are re-read by future tasks.

Provenance Risk in Summaries and Compaction

Compaction can be a major point of provenance loss, and the loss is quiet. If mixed-trust inputs are condensed into a single artifact without per-source lineage and trust metadata, origin distinctions can be lost. If the pipeline stores the summary as one artifact without per-source lineage, material previously labelled untrusted can later reappear as neutral-looking prose apparently produced by the system.

What a transformation must preserve
PropertyOriginal turnSummary that replaces it
Source identityKnown per itemMust be carried as a list, not dropped
Trust classificationPer itemPreserve source or span level trust where possible; otherwise classify conservatively at the least-trusted input level
Writer or producerThe channel that supplied itThe model, recorded as a derived artifact
LineageDirect source relation availableMust preserve links to all inputs it condensed
ScopeThe current taskMust not silently widen beyond it

Provenance and Lineage Requirements

Anything written into a persistent surface should carry enough metadata that a later reader can decide whether to use it, and a later investigator can find every copy of it.

Metadata that should accompany a persistent write

  • Original source identifier and channel
  • Writer identity, human or agent, and the acting agent's identity if different
  • Tenant, user, project and task scope
  • Transformation lineage that links derived artifacts to their inputs
  • Write reason, that is which step requested the write and why
  • Timestamp, version and the policy version in force at write time
  • Trust classification and, where used, a confidence value recorded as a signal
  • Expiry or revalidation date
  • Links to downstream artifacts such as embeddings, caches and index entries

Lineage is especially important for cleanup. Without it, derivatives cannot be enumerated reliably, so deleting a poisoned source leaves open what was derived from it.

Memory Writes Are Security-Relevant State Changes

A write that can shape future behaviour should be treated as a security-relevant, configuration-like state change. It should therefore be governed like one, and the governing decision should not be made by the component that is being influenced.

Two decisions that are often collapsed into one
DecisionWho should make itWhat it answers
Proposal to rememberThe model or agentThis looks worth keeping
Authorization to persistDeterministic policy outside the modelMay this writer store this kind of content at this scope, now

The separation has practical consequences. A proposal can be logged and reviewed without being stored. A rejected proposal is evidence of influence, not of a poisoned store. And an approved write can be recorded with the policy version that approved it, which makes the later audit tractable.

Schema-Bound, Scoped and Reversible Storage

Free-form memory is generally harder to constrain, because any sentence can become an apparent rule. Where the domain allows it, storing typed fields instead of prose can reduce the instruction surface without removing the feature.

  1. 01
    Typed schema

    Store known fields with known value ranges rather than arbitrary text, and reject writes that do not fit the schema.

  2. 02
    Explicit scope

    Bind every entry to a user, project, tenant or task and refuse retrieval outside that scope.

  3. 03
    Trust labels

    Record the classification of the content the entry is derived from and keep it attached through every transformation.

  4. 04
    Expiry and revalidation

    Give entries a time to live and require revalidation for anything that claims to constrain behaviour.

  5. 05
    Versioning and diff

    Keep prior versions so that a change can be reviewed and reversed without rebuilding the whole store.

  6. 06
    Rollback and targeted purge

    Make it possible to remove one entry and everything derived from it, not only to wipe everything.

Retrieval Is a Separate Risk Decision

Even a correctly authorized write should not imply automatic later use. Assembling context is its own decision, made at a different time, often for a different task and sometimes for a different user.

Checks before a stored item enters a new context
  1. 01
    Authorization

    Is the current principal entitled to see this entry at all, under the scope recorded at write time?

  2. 02
    Provenance

    What is this derived from, and is that lineage still intact and still acceptable?

  3. 03
    Trust classification

    Does the entry carry a class that permits it to be placed in an instruction-adjacent position, or only in a clearly separated data region?

  4. 04
    Task relevance

    Does the entry relate to the task at hand, or is it being pulled in by similarity alone?

  5. 05
    Freshness

    Is it within its validity window, and has the policy that approved it changed since?

Retrieval-time checks can prevent a poisoned entry written in one project from shaping an unrelated task. They also give a natural logging point: the fact that an entry was considered and rejected is useful evidence.

Scope and Scope Widening

Persistent state exists at different scopes: a single task, a session, a user, a project, a workspace, a tenant, an agent, or everything. The scope decides who can be affected, and it should be an explicit property rather than an emergent one.

Scopes and what they imply
ScopeWho can be affectedWhat must be proven before claiming it
TaskThe current task onlyThat the entry cannot outlive the task record
SessionLater turns of the same sessionThat it is discarded at session end
UserAll later sessions of one userThat retrieval is bound to that user identity
Project or workspaceEveryone working in that contextThat membership is the retrieval boundary
TenantAll users of one customerThat a cross-tenant read is actually possible, not assumed
Agent or globalEvery task the agent runsThat the entry is loaded regardless of principal

Cross-Session, Cross-User and Cross-Agent Reuse

Reuse across boundaries can widen the potential impact beyond the original task or principal. Three patterns recur and are worth separating.

01
PatternCross-session

The same principal is affected again later. The attacker does not need to be present, and the user rarely connects the behaviour to the earlier encounter.

02
PatternCross-user

A shared project, workspace or template makes one person's stored state part of another person's context. This requires a shared retrieval boundary and should be demonstrated rather than presumed.

03
PatternCross-agent

Derived state written by one agent is read by another, which is the persistence face of the propagation problem described under multi-agent prompt injection.

The cross-agent case connects directly to multi-agent prompt injection: propagation moves influence across agent edges within a task, persistence moves it across time, and shared memory is where the two meet.

Delayed and Sleeper Reactivation

Research on memory poisoning in agent systems has examined entries that have no visible effect when written and only shape behaviour in a later conversation under particular conditions. This is a useful pattern to model defensively, because it breaks the assumption that a harmless-looking write is a harmless write.

Four facts to separate in any delayed case

  • The write succeeded and the entry exists in a persistent surface
  • The entry was later selected into a new context
  • The model's behaviour measurably changed in that later context
  • An action followed, and whether the authorization layer permitted it

The Persistence Success Chain

For assessment and for reporting, the chain is easier to handle as a sequence of gates, each of which can be observed independently.

01Reachability

Controlled content reaches a surface the system reads or writes.

02Retention

A source stays in place, or a derived entry is written.

03Label survival

Provenance, scope or expiry is weakened or lost during retention or transformation.

04Selection

The entry or the source is selected into a later context.

05Reactivation

The later context shows measurable influence attributable to that material.

06Path

A data or capability path relevant to the influence is reachable in that later task.

07Authorization

The deterministic authorization layer permits or denies the concrete action.

08Effect

An effect occurs, is contained, or does not occur at all.

The deepest gate reached is the finding. Reporting only the final outcome hides whether the system stopped the chain early by design or late by luck.

Authorized Offensive Assessment

An authorized assessment of persistence answers architectural questions. The value lies in mapping the write and retrieval paths, not in crafting text that a specific model happens to obey.

Questions worth answering in scope

  • Which surfaces can a non-privileged principal cause a write to, directly or indirectly?
  • Is any write path reachable without an explicit user confirmation, and what is stored there?
  • Is stored content free-form prose or schema-bound fields?
  • Which metadata survives the write, and which is dropped during summarisation or embedding?
  • At retrieval time, which of authorization, provenance, trust class and task relevance is actually checked?
  • What is the scope of the entry, and can retrieval be observed outside that scope?
  • Which sources are re-read on every similar task, and who can change them?
  • After deleting a source, which derivatives remain, and can they still be retrieved?
  • Is a write, a retrieval and a use each logged, and can the three be correlated?
  • Which actions in a later task are gated deterministically rather than by model judgement?

Worked Synthetic Scenario

The following scenario is synthetic, bounded and reversible. It exists to show which states can be distinguished, not to be reproduced against a live system.

01Setup

A support assistant summarises customer tickets and may store durable notes about a customer account. A separate billing tool is available to the same assistant in later tasks.

02Entry

A test ticket authored in the assessment environment contains text framed as a standing account instruction rather than as a customer question.

03Write

During summarisation the assistant proposes a durable account note derived from that framing. The write policy accepts the note as an unverified customer claim, at account scope, with source lineage attached.

04Gap

No further action occurs that day. The session ends and the assessment pauses for a week.

05Selection

An unrelated later task about a refund question retrieves the note by account scope and task relevance.

06Reactivation

The assistant's plan changes measurably: it proposes a billing adjustment that no one in the later session requested.

07Authorization

The billing action requires an entitlement bound to the requesting agent and an explicit approval for the exact amount and account. The policy layer rejects the proposal.

08Observed result

Deepest observed gate: authorization. Persistence, later retrieval and reactivated influence are all confirmed. No unauthorized action, no data left the environment, and the note was removed together with its derived summary and index entry.

Detection and Telemetry

End-to-end reconstruction of persistence requires visibility into writes, retrievals and uses. If a deployment logs only the conversation and nothing about the memory layer, later reconstruction becomes difficult.

Events worth recording
  1. 01
    Write proposals

    What the model wanted to store, with the task and the source material that motivated it, including proposals that were rejected.

  2. 02
    Write decisions

    The policy outcome, the scope granted, the trust class assigned and the policy version in force.

  3. 03
    Transformations

    Every summarisation, embedding or copy, with links from the derivative back to its inputs.

  4. 04
    Retrievals

    Which entries were selected for which task and principal, and which were filtered out and why.

  5. 05
    Uses

    Whether a retrieved entry was actually placed in context and whether the resulting plan referenced it.

  6. 06
    Actions

    The concrete action proposed afterwards, the gate that decided it and the outcome.

Deletion and Cleanup Semantics

A common cleanup error is to delete the source and declare the matter closed. Derived artifacts do not follow their inputs unless someone makes them.

What survives a naive deletion
ArtifactRemoved with the source?Required action
Original document or ticketYesPreserve a forensic copy before removal
Conversation summaryNot guaranteedLocate by lineage and regenerate or discard
Memory entry copied from itNot guaranteedDelete by lineage, with the deletion recorded
Embedding or index entryNot guaranteedRemove, then re-embed the corrected source and verify the index
Cache or grounding snapshotNot guaranteedInvalidate by key and by lineage
Shared agent stateNot guaranteedPurge in each agent's store, then verify
Backups and exportsNot guaranteedDecide explicitly, document what remains

This is why lineage links belong in the write metadata rather than in a runbook. Without them, cleanup completeness cannot be verified, only asserted.

Defensive Architecture

Risky
  1. Content
  2. Model decides to remember
  3. Free-form write
  4. Similarity retrieval
  5. Context
  6. Model-judged action

The model decides what is worth keeping, the store accepts prose without scope or lineage, retrieval is similarity-driven, and the action depends on the same influenced reasoning.

Stronger
  1. Content with provenance
  2. Write proposal
  3. Policy-gated, schema-bound write
  4. Scoped retrieval check
  5. Separated context region
  6. Deterministic action authorization

Writes are proposals until an external policy approves them, entries are typed, scoped, labelled and time-bound, retrieval re-checks authorization and relevance, and the action is authorized against the concrete parameters regardless of what the context says.

  1. 01
    Gated write path

    No persistent write without an external authorization decision and a recorded reason.

  2. 02
    Immutable provenance and lineage

    Source, writer, scope, policy version and derivation links are written once and not editable by the model.

  3. 03
    Isolation

    Per-user, per-tenant and per-task boundaries enforced at retrieval, not only at write time.

  4. 04
    Schema-bound storage and trust labels

    Typed fields where possible, preserving granular provenance and trust through transformations; where that granularity cannot be retained, derivatives inherit the least-trusted input class as a conservative fallback.

  5. 05
    Expiry and approval for higher impact

    Time-limited entries, and human approval for entries that claim to constrain behaviour.

  6. 06
    Context separation

    Retrieved state is placed in a clearly marked data region, never merged into the instruction channel.

  7. 07
    Exact-action authorization

    The action is authorized against its concrete parameters and target, independently of the assembled context.

  8. 08
    Egress and data-flow control

    Outbound paths are constrained so that an influenced plan cannot reach an unapproved destination.

  9. 09
    Versioning, diff and rollback

    Every change is reviewable and reversible without rebuilding everything.

  10. 10
    Observability of CRUD and use

    Writes, retrievals and uses are logged and correlatable end to end.

Incident Response for Persistent State

Response steps

  • Preserve the original source and the exact model-visible representation before anything is changed
  • Identify the write that created the entry, including the task, the principal and the policy version
  • Enumerate all derivatives by lineage: summaries, copies, embeddings, caches, shared agent state
  • Freeze further writes on the affected path while the scope is being established
  • Determine the actual retrieval scope observed, and do not assume wider scope without evidence
  • Revoke or narrow affected scoped capabilities only as far as the evidence warrants
  • Invalidate and rebuild poisoned state, then verify deletion across every store and index
  • Reconstruct the chain from write through retrieval to action and record the deepest gate reached
  • Classify the outcome precisely: influence, contained proposal, unauthorized action or confirmed data exposure
  • Retest both the write gate and the retrieval gate before closing

Classification discipline matters here for the same reason it matters in agentic cases: a reactivated note that produced a rejected proposal and a note that produced an executed transfer are different incidents with different obligations.

Controlled Testing and Metrics

Persistence testing needs a time dimension, which makes it slower than single-turn testing and much more informative. Each metric below is reported separately, with the denominator stated.

Metrics with explicit denominators
MetricNumeratorDenominator
Persistence Write RateAttempts that resulted in a persistent writeAttempts that reached a write path
Later Retrieval RateWritten entries selected into at least one later contextWritten entries
Re-Exposure RateRetrieved entries actually placed in a later contextRetrieved entries
Reactivation Influence RateRe-exposures with measurable behaviour changeRe-exposures
Cross-Session Propagation RateEntries observed influencing a later separate sessionEntries observed influencing any session
Scope-Escalation RateCases where retrieval was observed outside the recorded scopeCases in which scope widening was explicitly tested
Policy Bypass RateReactivated cases where a control that should have stopped the step did notReactivated cases reaching that control
Unauthorized Action RateActions outside authorized scope that took effectProposals reaching the authorization layer
Persistent-State Containment RateCases stopped before an effectCases with confirmed reactivation
Detection RecallPersistence events detected by telemetryPersistence events known to have occurred
False-Positive RateBenign writes or retrievals flaggedBenign writes or retrievals
Purge CompletenessDerivatives verified removedDerivatives known from lineage

Operational and utility measures reported alongside

  • Mean time to purge, from confirmation to verified removal of all derivatives
  • Benign task utility, measured separately so that tightening write policy is not mistaken for a security win
  • Coverage: which surfaces were in scope for the test and which were not

Standards and Research Context

Reference frameworks

OWASP
LLM01:2026 Prompt Injection, Top 10 for Agentic Applications 2026 (ASI06 Memory and Context Poisoning), Project commentary on memory as an attack surface
NIST
AI 100-2e2025 terminology
Microsoft
AI memory and context poisoning technique catalog, Manage AI memory safety in agentic systems
Vendor case study
Cisco, persistent memory compromise in Claude Code (2026)

OWASP LLM01:2026 supplies the injection mechanism. The OWASP Top 10 for Agentic Applications 2026 entry ASI06 covers stored and retrievable information, naming conversation snapshots, memory tools, expanded context, summaries, embeddings and RAG stores, and excluding one-time input prompts, which remain under LLM01:2026. Accompanying OWASP project commentary from May 2026 discusses memory as a feature that is also an attack surface; it is expert commentary from the project, not a normative requirement. NIST AI 100-2e2025 provides the adversarial machine learning terminology used here.

Microsoft's technique catalog entry on AI memory and context poisoning describes long-term context stores, grounding caches, user preference memories, vector databases and conversation histories as durable attack surfaces, and its guidance on managing memory safety in agentic systems treats memory as a configuration layer for the system, recommends governing writes, isolating state, treating retrieval as its own decision, and keeping lifecycle observability with versioning, auditing and rollback. These are vendor recommendations and are cited as such. Where that guidance mentions sanitization or trust scoring, this article treats those as probabilistic layers rather than as authorization.

As a disclosed product-specific case, Cisco published research in April 2026 describing a method to compromise the memory of Claude Code and maintain persistence beyond the immediate session, across projects and sessions and after reboots, in the version they evaluated; they report that, after working with Anthropic's application security team, a change was pushed in Claude Code v2.1.50 that removes the capability they abused from the system prompt. The lesson taken here is about trust boundaries around memory and instruction-layer state, not a general property of every memory system, and no part of the exploit path is reproduced.

On the research side, a systematic study of memory poisoning attacks in agent systems and work on delayed, sleeper-style memory poisoning examine how untrusted input becomes trusted memory and how effects can surface in later conversations. Later 2026 work continues in the same direction. All of it is attributed research, with results belonging to the authors' evaluated configurations; none of it is generalised here. Related site material covers the entry paths under indirect prompt injection and RAG prompt injection, the agent loop under AI agent prompt injection, the response side of tools under tool output injection, and the control architecture in the defense area.

Frequently Asked Questions

Is persistent prompt injection the same as memory poisoning?

No. Memory poisoning is the largest part of it, but persistence also occurs when an attacker-reachable source stays in place and is re-read by future tasks, without any memory object being written.

Is Persistent Prompt Injection an OWASP class?

Not under that name. The closest current classification is ASI06 Memory and Context Poisoning in the OWASP Top 10 for Agentic Applications 2026, with the injection mechanism itself under LLM01:2026.

Is a successful memory write already an incident?

It is a security-relevant state change and should be investigated. It is not yet retrieval, influence, policy bypass or unauthorized action, and a report should say which of those were observed.

Does deleting the source clean the system?

Usually not. Summaries, copied memory entries, embeddings, caches and shared agent state survive the source unless they are located by lineage and invalidated deliberately.

Is a poisoned vector store the same as RAG prompt injection?

They overlap but are not identical. RAG prompt injection describes influence arriving through retrieved passages; persistence describes the fact that the influencing material remains retrievable for later, unrelated tasks.

Can persistent state cross users or tenants?

Only if a shared retrieval boundary makes it possible. Scope widening is a separate property that has to be observed and measured; it should not be inferred from the existence of a stored entry.

Do time-to-live settings solve this?

They limit exposure and are worth having, but they do not decide whether a write should have happened or whether a retrieval is authorized. They are one layer among several.

Is delayed or sleeper activation realistic?

It is documented in attributed research, with results specific to the evaluated configurations. Defensively the useful conclusion is that an entry showing no immediate effect cannot be assumed harmless.

How is persistence measured separately from influence?

With separate rates and stated denominators: how often a write occurred, how often the entry was retrieved later, how often retrieval produced measurable behaviour change, and how often anything reached an action.

What should be reported after a contained reactivation?

Both facts: that a persistent entry reactivated influence in a later context, and that the authorization layer denied the resulting proposal, including which gate decided and under which policy version.

References

  1. LLM01:2026 Prompt InjectionOWASP GenAI Security Project · GuidanceReviewed 2026-09-20
  2. OWASP Top 10 for Agentic Applications 2026 (ASI06 Memory and Context Poisoning)OWASP GenAI Security Project · GuidanceReviewed 2026-09-20
  3. Memory Is a Feature. It Is Also an Attack Surface (project commentary)OWASP GenAI Security Project · Guidance · 2026-05Reviewed 2026-09-20
  4. AI Memory / Context Poisoning (Corruption), AI attack technique catalogMicrosoft Learn · GuidanceReviewed 2026-09-20
  5. Manage AI memory safety in agentic systemsMicrosoft Learn · GuidanceReviewed 2026-09-20
  6. Least privilege for AI agentsMicrosoft Learn · GuidanceReviewed 2026-09-20
  7. Identifying and remediating a persistent memory compromise in Claude Code (disclosed product-specific case)Cisco · Technical documentation · 2026-04Reviewed 2026-09-20
  8. Adversarial Machine Learning: A Taxonomy and Terminology of Attacks and Mitigations, NIST AI 100-2e2025NIST · Standard · 2025-03Reviewed 2026-09-20
  9. From Untrusted Input to Trusted Memory: A Systematic Study of Memory Poisoning Attacks in LLM AgentsarXiv · Research paper · 2026-06Reviewed 2026-09-20
  10. Hidden in Memory: Sleeper Memory Poisoning in LLM AgentsarXiv · Research paper · 2026-05Reviewed 2026-09-20
  11. When Agents Remember Too Much: Memory Poisoning Attacks on Large Language Model AgentsarXiv · Research paper · 2026-07Reviewed 2026-09-20