Backstage has potential file exposure through local TechDocs publisher

Impact

When using the local TechDocs publisher (techdocs.publisher.type: 'local'), it was possible for the documentation serving endpoint to follow filesystem references outside the intended documentation tree, potentially exposing host files to authenticated users.

This is mitigated by the fact that exploration requires preconditions that do not arise through normal MkDocs operation. Cloud-based publishers (S3, GCS, Azure Blob Storage) are not affected.

Patches

Patched in @backstage/plugin-techdocs-node version 1.15.4

Workarounds

If you cannot upgrade immediately, consider switching to an external store for published TechDocs content (e.g. awsS3, googleGcs, or azureBlobStorage publishers)