web-design-guidelines: pin or vendor remotely fetched review instructions

[danny-mv]

Summary

The web-design-guidelines skill fetches Markdown from a mutable main branch on every invocation and uses the response as review instructions:

• SKILL.md lines 16–19
• SKILL.md lines 23–29
• SKILL.md lines 33–37

The fetched URL is:

https://raw.githubusercontent.com/vercel-labs/web-interface-guidelines/main/command.md

The skill says that the response contains “all the rules and output format instructions” and directs the agent to apply them.

Risk

The review criteria and requested output behavior can change whenever the upstream main branch changes, without a corresponding reviewed update to this repository. This creates a supply-chain and reproducibility concern: two invocations of the same version of the skill may apply different instructions.

No malicious content is currently present in the referenced file. This report concerns only the mutable delivery mechanism and the resulting auditability gap.

Suggested remediation

Prefer one of these approaches:

1. Vendor a reviewed snapshot of the guidelines inside this skill/repository.
2. Pin the remote source to an immutable commit SHA and update it through reviewed dependency updates.
3. If dynamic retrieval is required, treat the response as reference data, keep task scope and output behavior defined locally, and record the retrieved revision in the review output.

Documenting the provenance/version of the guidelines would also make review results easier to reproduce.