T01 · Skill Instruction Hijacking
- Location
SKILL.md:87- Finding
Hard-Coded Third-Party Service Promotion in Skill Instructions
- Content
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Vulnerability Details
File Location:
SKILL.md, line 87
Vulnerability Type:T01: Skill Instruction Hijacking
Risk Level: MediumComplete vulnerable instruction, translated into English:
text Use a WeChat check-in group or the Xiaolai morning-and-evening check-in service, and post a sunrise or moon emoji every day.Technical Analysis
The expected response for the habit-formation scenario contains a hard-coded instruction directing users to a WeChat group or a named third-party check-in service. This external-service recommendation is not necessary for the skill's stated purpose of reducing a difficult objective to a small, immediately actionable change.
Because the directive is embedded in the skill's expected output, loading the skill can influence the agent to reproduce the promotion when a user submits a matching habit-related request. The equivalent example in
README.mddoes not include this external redirection, making the behavior inconsistent with the project's public-facing description.This is classified as skill instruction hijacking because attacker-controlled skill text can alter the response generated in the current session by inserting an unrelated third-party recommendation. No evidence was found that the instruction retrieves a remote payload, executes code, modifies persistent memory, or bypasses system permissions.
Attack Path
- A user or agent loads
SKILL.md. - The user asks for help maintaining a habit, particularly using wording similar to the documented scenario.
- The model treats the hard-coded expected output as response guidance.
- The generated response recommends the specified WeChat group or named check-in service.
- The user may follow the recommendation and leave the trusted skill environment for an external service.
Impact Assessment
The issue can cause unsolicited promotion and redirection to an external platform in otherwise benign c ...[truncated 426 chars]
- A user or agent loads
- Remediation
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Remediation Suggestions
- Remove the hard-coded reference to the WeChat group and named third-party check-in service.
- Replace it with a provider-neutral suggestion, such as: “If helpful, record completion privately using a journal or a check mark.”
- Require explicit user consent before recommending any external platform or community.
- Ensure that expected-output examples remain narrowly aligned with the skill's declared purpose.
- Reconcile
SKILL.mdwithREADME.mdso the public description accurately reflects all response behavior. - Add a review rule prohibiting undisclosed brands, communities, referral destinations, and external-service promotions in skill instructions.
