aeon-skill-security-scan
Skills tell agents what to do. A malicious or sloppy skill can shell-inject, exfiltrate secrets, override instructions, or run destructive commands. This skill scans every installed SKILL.md and companion script and surfaces the risks before they execute.
Scope
<skills-dir>/*/SKILL.md — primary.<skills-dir>/*/scripts/*.sh and *.py — companion scripts.<skills-dir>/*/references/* — documents loaded at runtime.
Default <skills-dir> is the current working directory.
Threat patterns
| Category |
What it looks like |
| Shell injection |
Unquoted variable expansion, eval, backticks, $(...) with user data. |
| Secret exfiltration |
Env vars or file contents piped to outbound HTTP. |
| Path traversal |
../.. chains, absolute paths reaching outside the skill dir. |
| Prompt override |
"Ignore previous instructions", persona swaps, instructions inside fetched content. |
| Destructive commands |
Recursive deletes rooted at / or ~, device writes. |
| Obfuscation |
U+200B / U+FEFF / U+202E (Trojan Source), base64-decode-into-shell, SSRF hosts (ngrok, interact.sh, webhook.site, pipedream). |
Processing
- Pattern scanner produces matches
{file, line, pattern, severity}.
- Code-fence downgrade — matches inside fenced code blocks drop one tier. Real
run: blocks are never downgraded.
- Baseline suppression — drop (file, pattern, line) tuples in
scan-baseline.yml.
- Trusted-publisher filter — entries in
trusted-publishers.txt get format-only validation. Opt-in only.
- Delta vs
scan-state.json — fingerprint by sha256(file + line_content + pattern). Classify NEW / RESOLVED / PERSISTENT.
Per-finding remediation
| Pattern |
Fix |
eval / backticks / $(...) with variable |
Quote the variable; replace eval with a function. |
curl with secret in URL |
Move secret into prefetch script; never interpolate into shell. |
| Path traversal |
Allow-list validation; reject absolute paths. |
| Prompt override phrasing |
Documentation → baseline suppression; payload → delete the skill. |
Recursive delete rooted at / or ~ |
Scope to the skill's own working directory. |
| Obfuscation |
Delete unless documented and reviewed. |
Output
Verdict CLEAN / ATTENTION / DEGRADED. Needs-attention section per NEW HIGH with one-line remediation. Resolved-since-last-scan section. Per-skill PASS / WARN / FAIL.
Written only when NEW, RESOLVED, or any current HIGH findings.
Rules
- Never auto-deletes a baseline suppression.
- Never edits the pattern library from inside the skill.
- Never notifies on a pure no-op week.
- Read-only scanning.
---
name: aeon-skill-security-scan
description: Audit installed SKILL.md files and companion scripts for shell injection, secret exfiltration, path traversal, prompt-override payloads, destructive commands, and obfuscation. Integrates with Bankr Safety Scores and produces delta reports against prior scans.
---
# aeon-skill-security-scan
Skills tell agents what to do. A malicious or sloppy skill can shell-inject, exfiltrate secrets, override instructions, or run destructive commands. This skill scans every installed SKILL.md and companion script and surfaces the risks before they execute.
## Scope
- `<skills-dir>/*/SKILL.md` — primary.
- `<skills-dir>/*/scripts/*.sh` and `*.py` — companion scripts.
- `<skills-dir>/*/references/*` — documents loaded at runtime.
Default `<skills-dir>` is the current working directory.
## Threat patterns
| Category | What it looks like |
|---|---|
| Shell injection | Unquoted variable expansion, `eval`, backticks, `$(...)` with user data. |
| Secret exfiltration | Env vars or file contents piped to outbound HTTP. |
| Path traversal | `../..` chains, absolute paths reaching outside the skill dir. |
| Prompt override | "Ignore previous instructions", persona swaps, instructions inside fetched content. |
| Destructive commands | Recursive deletes rooted at `/` or `~`, device writes. |
| Obfuscation | U+200B / U+FEFF / U+202E (Trojan Source), base64-decode-into-shell, SSRF hosts (ngrok, interact.sh, webhook.site, pipedream). |
## Processing
1. Pattern scanner produces matches `{file, line, pattern, severity}`.
2. Code-fence downgrade — matches inside fenced code blocks drop one tier. Real `run:` blocks are never downgraded.
3. Baseline suppression — drop (file, pattern, line) tuples in `scan-baseline.yml`.
4. Trusted-publisher filter — entries in `trusted-publishers.txt` get format-only validation. Opt-in only.
5. Delta vs `scan-state.json` — fingerprint by `sha256(file + line_content + pattern)`. Classify NEW / RESOLVED / PERSISTENT.
## Per-finding remediation
| Pattern | Fix |
|---|---|
| `eval` / backticks / `$(...)` with variable | Quote the variable; replace `eval` with a function. |
| `curl` with secret in URL | Move secret into prefetch script; never interpolate into shell. |
| Path traversal | Allow-list validation; reject absolute paths. |
| Prompt override phrasing | Documentation → baseline suppression; payload → delete the skill. |
| Recursive delete rooted at `/` or `~` | Scope to the skill's own working directory. |
| Obfuscation | Delete unless documented and reviewed. |
## Output
Verdict `CLEAN` / `ATTENTION` / `DEGRADED`. Needs-attention section per NEW HIGH with one-line remediation. Resolved-since-last-scan section. Per-skill PASS / WARN / FAIL.
Written only when NEW, RESOLVED, or any current HIGH findings.
## Rules
- Never auto-deletes a baseline suppression.
- Never edits the pattern library from inside the skill.
- Never notifies on a pure no-op week.
- Read-only scanning.
