Trust Assessment
fly-machines received a trust score of 13/100, placing it in the Untrusted category. This skill has significant security findings that require attention before use in production.
SkillShield's automated analysis identified 4 findings: 2 critical, 2 high, 0 medium, and 0 low severity. Key findings include Arbitrary command execution, Remote code execution: curl/wget pipe to shell, Potential Command Injection in `BOT_ID` variable interpolation.
The analysis covered 4 layers: Manifest Analysis, Static Code Analysis, Dependency Graph, LLM Behavioral Safety. All layers scored 70 or above, reflecting consistent security practices.
Last analyzed on February 14, 2026 (commit 13146e6a). SkillShield performs automated 4-layer security analysis on AI skills and MCP servers.
Layer Breakdown
Behavioral Risk Signals
Security Findings4
| Severity | Finding | Layer | Location | |
|---|---|---|---|---|
| CRITICAL | Arbitrary command execution Remote code download piped to interpreter Review all shell execution calls. Ensure commands are static (not built from user input), use absolute paths, and are strictly necessary. Prefer library APIs over shell commands. | Manifest | skills/mrgoodb/fly-machines/SKILL.md:268 | |
| CRITICAL | Remote code execution: curl/wget pipe to shell Detected a pattern that downloads and immediately executes remote code. This is a primary malware delivery vector. Never pipe curl/wget output directly to a shell interpreter. | Static | skills/mrgoodb/fly-machines/SKILL.md:268 | |
| HIGH | Potential Command Injection in `BOT_ID` variable interpolation The `BOT_ID` variable in the 'Deploy a bot instance' example is directly interpolated into a `curl -d` argument using shell string concatenation (`'"$BOT_ID"'`). If `BOT_ID` is derived from untrusted user input, an attacker could inject arbitrary shell commands that would be executed by the shell before the `curl` command runs, leading to remote code execution. Sanitize or escape any user-provided input used to construct shell commands, especially when interpolating variables into single-quoted strings. For JSON payloads, ensure that values are properly JSON-encoded and not directly shell-interpolated. Consider using a dedicated JSON parsing tool or library to construct payloads safely. | LLM | SKILL.md:146 | |
| HIGH | Unsafe `flyctl` installation method (Supply Chain Risk) The recommended installation method for `flyctl` (`curl -L https://fly.io/install.sh | sh`) pipes a script downloaded from the internet directly into a shell. This practice is inherently risky as it executes code from an external source without prior inspection or verification. A compromise of `fly.io`'s infrastructure or the `install.sh` script could lead to arbitrary code execution on the system where this command is run. Avoid piping arbitrary scripts from the internet directly to `sh`. Recommend alternative installation methods such as package managers (if available), verifying script checksums, or reviewing the script content before execution. If direct execution is necessary, ensure the source is highly trusted and consider sandboxing the execution environment. | LLM | SKILL.md:175 |
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