Keep real API keys out of source files and out of any context a coding assistant can read. Have generated code obtain credentials from a controlled runtime environment or secrets manager, limit access to what the task needs, and scan changes before they are committed or merged. Treat scanning and repository push protection as backstops—not guarantees. If a real key is exposed, revoke or rotate it and investigate its use.
Why “default to secret” is the safer rule
Assume a credential could be exposed if it enters a coding assistant’s readable files, prompt, terminal context, or workflow. The most reliable first step is to keep the credential out of those places, rather than asking a model to protect it after seeing it.
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A prompt is not an authorization boundary or a secret store. OWASP’s guidance on system prompt leakage says, “The system prompt should not be considered a secret, nor should it be used as a security control.” Keep access controls outside the model and do not grant an agent credentials it does not need. OWASP, LLM07:2025 System Prompt Leakage
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Keep credentials out of the assistant’s context
Do not paste a live key into a prompt or leave it in a project file the assistant can read. OWASP recommends using vault services or encrypted stores for secrets and excluding sensitive files from coding-assistant context. OWASP Secrets Management Cheat Sheet and OWASP, LLM06:2025 Excessive Agency
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Use the coding tool’s context-exclusion mechanism for files such as .env, private keys, and credential files. Do not rely on .gitignore for this: it controls what Git tracks, not what a filesystem-reading assistant can open.
In prompts and examples, use a placeholder such as API_KEY or a configuration-variable name, not the actual credential. If an agent has tool, repository, or CI access, limit its permissions and require approval before it reaches sensitive resources or changes workflows.
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Make generated code retrieve secrets at runtime
Ask the assistant to write code that reads a credential from a controlled runtime environment or retrieves it through a secrets manager integration. Provide only the access the workload needs, and avoid printing secret values or including them in exception messages. OWASP’s secrets-management guidance covers least-privilege access and runtime secret provisioning.
For example, a prompt can ask for code that reads API_KEY from the process environment, without supplying its value. The deployment environment—not the source file or prompt—must provide the real credential. Where a secrets manager is used, evaluate whether its access controls, rotation and revocation support, audit visibility, deployment integration, and operational requirements fit the workload.
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Review changes and block accidental leaks
Use more than one check: inspect the change yourself, scan locally before committing, and run secret detection as a pull request gate configured to fail when it finds a credential. Review source code, tests, examples, notebooks, logs, and CI configuration for hard-coded values or accidental secret forwarding.
Enable repository push protection where available. GitHub says, “With push protection, secret scanning blocks contributors from pushing secrets to a repository and generates an alert whenever a contributor bypasses the block.” GitHub Docs: How-tos for leak prevention
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Push protection and scanners recognize supported secret patterns; they cannot establish that every possible credential or leak path is covered. When assessing checks, consider which secret types they detect, when they run, how findings and bypasses are handled, and whether the enforcement is available for the repository. Keep scanning in the development workflow even when push protection is enabled.
Respond promptly if a real key appears
- Revoke or rotate the exposed credential. Treat it as compromised; deleting the line from the current file does not make the key safe.
- Remove it from active code and configuration. Check the repository’s secret alerts and review available access logs for unexpected use.
- Check the surrounding workflow. Look for copies in tests, examples, notebooks, logs, CI configuration, prompts, or other files the assistant could read, then close the access path that allowed the exposure.
OWASP’s secrets-management guidance includes revocation, rotation, and monitoring as parts of the secret lifecycle. OWASP Secrets Management Cheat Sheet
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Choose controls for both storage and detection
Runtime secret storage and leak detection address different parts of the problem. Choose storage based on access control, least privilege, rotation and revocation, audit visibility, integration with deployment, and operational complexity. Choose scanning based on developer feedback, pull request enforcement, coverage of relevant secret types, bypass and audit handling, and repository availability. Neither choice removes every route by which a key can enter model context or generated output.
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