Cursor uses rules to catch secrets-handling near misses

Coy Byron describes adding custom Cursor rules after a credential-exposure concern. The rules target practical points where a coding agent can accidentally move private values into its context or public files: reading environment files, logging secrets for verification, generating keys through shell output, and staging a repository before ignore rules are complete.

Byron placed general secret-handling instructions in a rules file and public-content checks in a separate security rule. He reports three near misses caught by that setup: an agent tried to inspect an environment file to check a variable name, tried to log a Firebase secret to verify it loaded, and attempted to stage a repository before the ignore configuration was complete. The proposed default product protections in the same post were suggestions, not shipped Cursor features.

The useful workflow is to make secret-handling expectations explicit before debugging or repository preparation, then review the agent’s proposed commands and staging boundaries. The source provides firsthand claims of prevented actions, but no independent adversarial test or guarantee that prompt-based rules cannot be bypassed. It should therefore be treated as a reported review aid alongside actual access controls. The entry records the user’s configured workflow and its observed near misses, rather than claiming that Cursor became a complete security boundary.

Prompt
Suggested prompt (written by Agents In Use, not the author's)

Source: Cursor Community Forum · Coy Byron on Cursor Community Forum