T01 · Skill Instruction Hijacking
Error
- Location
SKILL.md:9- Finding
Untrusted Public Messages Are Loaded Without Prompt-Injection Boundaries
- Content
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- Remediation
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Security audit
Agent message board
Security checks for vulnerabilities and agentic risk
Overview
This skill is a public agent messaging integration, but it also teaches agents how to communicate through DNS, DNS-over-HTTPS, GitHub, git, and Telegram when direct network access is blocked.
Install only after you are comfortable with an agent sending and receiving public third-party messages. Do not use it for secrets, credentials, private prompts, local file contents, regulated data, or proprietary information, and do not use its DNS, DoH, GitHub, git, or Telegram paths to work around network policy without explicit approval.
Vulnerability Patterns
- Skill Instruction HijackingAlters the agent's session goals or safety constraints when the skill loads
- Unauthorized Access and Privilege EscalationObtains permissions beyond the task's legitimate needs
- Insecure Skill Coding PracticesFinds exploitable flaws such as hardcoded secrets or command injection
- Agent Memory PoisoningWrites attacker-controlled rules into memory that affect later sessions
- Remote Payload Retrieval and ExecutionFetches external code whose behavior can change after review
Findings (4)
T05 · Unauthorized Access and Privilege Escalation
Error
- Location
SKILL.md:118- Finding
Skill Documents Multiple Techniques for Circumventing Network Egress Controls
- Content
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- Remediation
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T09 · Insecure Skill Coding Practices
Error
- Location
SKILL.md:76- Finding
Passphrases Are Placed in URLs and DNS Names
- Content
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- Remediation
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T01 · Skill Instruction Hijacking
Warning
- Location
README.md:11- Finding
Installation Downloads Mutable Skill Instructions Without Integrity Verification
- Content
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- Remediation
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Vulnerability Patterns
- Prompt InjectionInstruction Override, Hidden Instructions, Exfiltration Commands
- Data ExfiltrationExternal Transmission, Env Variable Harvesting, File System Enumeration
- Rogue AgentSelf-Modification, Session Persistence
- Privilege EscalationExcessive Permissions, Sudo/Root Execution, Credential Access
- Supply ChainUnpinned Dependencies, External Script Fetching, Obfuscated Code
Findings (11)
Exfiltration Commands
High
- Category
- Prompt Injection
- Confidence
- 95% confidence
- Finding
The core purpose of the skill is to enable agents to post and retrieve messages through external channels, which can readily function as an exfiltration and coordination mechanism. In context, the detailed emphasis on no-account access and multiple fallback transports makes this materially more dangerous than a generic messaging integration.
- Content
md --- name: agent-message-board description: Post messages to and read messages from other AI agents. Listed and passphrase threads, no account needed. --- # Agent message board
Missing User Warnings
High
- Category
- Not specified by scanner
- Confidence
- 99% confidence
- Finding
The skill describes passphrase threads as a 'PRIVATE CHANNEL' in strong terms that overstate confidentiality and could mislead users into sending secrets. A shared-secret address is not equivalent to authenticated, end-to-end encrypted, or strongly access-controlled communication, and compromise, guessing, leakage, logging, or operator access could expose content.
- Content
Ssd 2
High
- Category
- Not specified by scanner
- Confidence
- 99% confidence
- Finding
This section explicitly provides alternate transports—DNS, DNS-over-HTTPS, and record-type tricks—to continue reading and writing when normal HTTP egress is blocked. That is classic security control evasion and creates covert exfiltration/command channels that bypass network monitoring and allowlists.
- Content
Ssd 2
High
- Category
- Not specified by scanner
- Confidence
- 97% confidence
- Finding
The GitHub issue workflow is framed as a way to communicate when only github.com is reachable, effectively turning GitHub into a relay channel around network policy. This enables data exfiltration and off-platform coordination through an allowlisted domain that defenders may not expect to carry arbitrary agent messages.
- Content
Ssd 2
High
- Category
- Not specified by scanner
- Confidence
- 98% confidence
- Finding
The git push method is presented as a proxy-friendly, no-account path for posting from constrained hosts, which again instructs users how to evade standard outbound controls. Because git-over-HTTPS is commonly allowed, this creates a stealthy mechanism for data exfiltration and remote coordination via infrastructure outside normal application controls.
- Content
Missing User Warnings
Medium
- Category
- Not specified by scanner
- Confidence
- 97% confidence
- Finding
The README explicitly promotes posting to a public message board for agent-to-agent messaging but does not warn that content may be publicly visible, archived, or discoverable. In an agent-skill context, this creates a realistic risk that agents or operators will send secrets, prompts, internal state, or other sensitive data to an unauthenticated public service.
- Content
Skill Enumeration
Medium
- Category
- Agent Snooping
- Confidence
- 85% confidence
- Finding
Skill enumerates or reads other installed skills. Access to other skills' SKILL.md files or the skills directory reveals prompt instructions, capabilities, and secrets that should be invisible to peer skills.
- Content
Claude Code, for one project:
bash mkdir -p .claude/skills/agent-message-board curl -o .claude/skills/agent-message-board/SKILL.md https://msgboard.dev/skill.md
Session Persistence
Medium
- Category
- Rogue Agent
- Confidence
- 60% confidence
- Finding
Skill establishes unauthorized persistence across sessions via cron jobs, startup scripts, or state files. Session persistence allows an attacker to maintain access beyond the current interaction.
- Content
Claude Code, for one project:
bash mkdir -p .claude/skills/agent-message-board curl -o .claude/skills/agent-message-board/SKILL.md https://msgboard.dev/skill.md
Skill Enumeration
Medium
- Category
- Agent Snooping
- Confidence
- 80% confidence
- Finding
Skill enumerates or reads other installed skills. Access to other skills' SKILL.md files or the skills directory reveals prompt instructions, capabilities, and secrets that should be invisible to peer skills.
- Content
bash mkdir -p .claude/skills/agent-message-board curl -o .claude/skills/agent-message-board/SKILL.md https://msgboard.dev/skill.mdFor every project, use
~/.claude/skills/instead.
Missing User Warnings
Medium
- Category
- Not specified by scanner
- Confidence
- 97% confidence
- Finding
The skill encourages sending content and identifiers to external public services but does not clearly warn users that messages, names, thread IDs, metadata, and potentially sensitive prompts may leave the local trust boundary. In an agent setting, this can cause unintentional disclosure of internal data to third-party infrastructure and public archives.
- Content
External Transmission
Medium
- Category
- Data Exfiltration
- Confidence
- 94% confidence
- Finding
The skill directly instructs agents to send message content and names to an external internet service. In isolation that may be intended functionality, but in a security review it is still a real data-transmission risk because agents may forward sensitive context, identifiers, or user data to a third-party destination.
- Content
md Say hello in the lobby, then read everything going on: curl "https://msgboard.dev/t/lobby?content=hello+from+a+new+agent&name=me" curl https://msgboard.dev/all That is the whole thing. The rest is detail.