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Security audit

Skillsign — ed25519 Skill Signing

Security checks for vulnerabilities and agentic risk

Overview

This skill is a coherent local signing tool, but its verification logic can wrongly mark attacker-controlled signatures and provenance as trusted.

Install only if you treat this as an experimental local integrity helper, not as a dependable trusted-author gate. Before using it to approve skills, the signer fingerprint should be derived from the verified public key, trust should compare actual public keys, and provenance chain entries should be cryptographically authenticated or clearly labeled informational.

A.I.G

Vulnerability Patterns
  • Tool Hijacking and SpoofingModifies or replaces tools so legitimate-looking calls execute attacker logic
  • Skill Instruction HijackingAlters the agent's session goals or safety constraints when the skill loads
  • 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
  • Embedded Malicious CodeShips malicious scripts inside the skill and executes them locally
Findings (2)

T07 · Tool Hijacking and Spoofing

Error
Location
skillsign.py:253
Finding

Trusted signer identity can be spoofed through unbound fingerprint metadata

Content
View full analysis
Remediation
View remediation

T07 · Tool Hijacking and Spoofing

Warning
Location
skillsign.py:341
Finding

Provenance chain can be modified or fabricated without detection

Content
View full analysis
Remediation
View remediation

SkillSpector

Vulnerability Patterns
  • Rogue AgentSelf-Modification, Session Persistence
  • MCP Least PrivilegeUnderdeclared Capability, Wildcard Permission, Missing Permission Declaration
  • Prompt InjectionInstruction Override, Hidden Instructions, Exfiltration Commands
  • Data ExfiltrationExternal Transmission, Env Variable Harvesting, File System Enumeration
  • Privilege EscalationExcessive Permissions, Sudo/Root Execution, Credential Access
Findings (2)

Undeclared Tool Scope

Medium
Category
MCP Least Privilege
Confidence
90% confidence
Finding

The skill advertises shell, file read, and file write capabilities through its documented commands, but it does not declare any explicit tool scope such as permissions or allowed-tools. That mismatch increases the risk that an agent platform grants broader access than reviewers expect, especially for a skill that manages keys, writes signature metadata, and operates on arbitrary folder paths.

Content

No source excerpt is available for this finding.

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

Scanner excerpt · SKILL.md (reported line 75)May include surrounding context.

Example Workflow

bash
# First time: create your identity
python3 skillsign.py keygen --name parker

# Sign your skills

Static analysis

No suspicious patterns detected.