Advisories for Npm/@Backstage/Plugin-Proxy-Backend package

An operator can configure overlapping proxy paths with different credential requirements. When a parent path permits unauthenticated access and a nested path requires credentials, the parent exemption can also cover requests handled by the nested proxy. An unauthenticated caller may therefore reach the nested upstream through Backstage, including with static upstream credentials configured for that proxy. Exploitation requires this specific overlapping route configuration. The resulting confidentiality and integrity impact depends …

An authenticated Backstage user could craft a request URL that causes the proxy-backend to forward the request to a path outside the configured base path on the target server. This is limited to target servers already configured as proxy endpoints and requires Backstage authentication by default.