@backstage/plugin-techdocs-node vulnerable to arbitrary code execution via MkDocs hooks

Impact

When TechDocs is configured with runIn: local, a malicious actor who can submit or modify a repository's mkdocs.yml file can execute arbitrary Python code on the TechDocs build server via MkDocs hooks configuration.

Patches

Upgrade to @backstage/plugin-techdocs-node version 1.13.11, 1.14.1 or later.
The fix introduces an allowlist of supported MkDocs configuration keys. Unsupported configuration keys (including hooks) are now removed from mkdocs.yml before running the generator, with a warning logged to indicate which keys were removed.

Note: Users of @techdocs/cli should also upgrade to the latest version, which includes the fixed @backstage/plugin-techdocs-node dependency.

Workarounds

If you cannot upgrade immediately:

1. Use Docker mode with restricted access: Configure TechDocs with runIn: docker instead of runIn: local. This provides container isolation, though it does not fully mitigate the risk.
2. Restrict repository access: Limit who can modify mkdocs.yml files in repositories that TechDocs processes. Only allow trusted contributors.
3. Manual review: Implement PR review requirements for changes to mkdocs.yml files to detect malicious hooks configurations before they are merged.
4. Downgrade MkDocs: Use MkDocs < 1.4.0 (e.g., 1.3.1) which does not support hooks. Note: This may limit access to newer MkDocs features.

Note: Building documentation in CI/CD pipelines using @techdocs/cli does not mitigate this vulnerability, as the CLI uses the same vulnerable @backstage/plugin-techdocs-node package.

References

MkDocs Hooks Documentation
MkDocs 1.4 Release Notes
TechDocs Architecture