The Agent Skills Directory

[DYNAMIC_CONTEXT_INJECTION]: The skill uses the !command`` syntax in SKILL.md to execute shell commands at load time. Specifically, it executes !"echo \"Loaded at $(date '+%Y-%m-%dT%H:%M:%S') — first arg is: $0\"" which directly incorporates the user-supplied argument $0 into a shell command string. While this specific example is used for testing and is relatively benign (echoing a timestamp), the pattern of passing $ARGUMENTS or $0 through $N syntax into a load-time shell command constitutes a command injection surface if the input is not strictly validated. This allows arbitrary shell execution if a user provides arguments containing command separators or subshells (e.g., ;/usr/bin/id).
[COMMAND_EXECUTION]: The skill documents and demonstrates the execution of shell commands at runtime. Although the current commands are for demonstration (e.g., date, echo), the underlying capability allows for broader system interactions triggered simply by loading the skill. The analysis identifies that the author is using this as a 'living test harness' to teach other developers how to avoid variable corruption, but the inclusion of active command substitution with user-controllable arguments remains a significant security surface area.

example-argument-substitution