`@backstage/backend-common` is a common functionality library for backends for Backstage, an open platform for building developer portals. In `@backstage/backend-common` prior to versions 0.21.1, 0.20.2, and 0.19.10, paths checks with the `resolveSafeChildPath` utility were not exhaustive enough, leading to risk of path traversal vulnerabilities if symlinks can be injected by attackers. This issue is patched in `@backstage/backend-common` versions 0.21.1, 0.20.2, and 0.19.10.
https://github.com/backstage/backstage/security/advisories/GHSA-2fc9-xpp8-2g9h
https://github.com/backstage/backstage/commit/edf65d7d31e027599c2415f597d085ee84807871
https://github.com/backstage/backstage/commit/78f892b3a84d63de2ba167928f171154c447b717
https://github.com/backstage/backstage/commit/1ad2b1b61ebb430051f7d804b0cc7ebfe7922b6f