CVE-2026-33528: Improper Limitation of a Pathname to a Restricted Directory

GoDoxy is a reverse proxy and container orchestrator for self-hosters. Prior to version 0.27.5, the file content API endpoint at `/api/v1/file/content` is vulnerable to path traversal. The `filename` query parameter is passed directly to `path.Join(common.ConfigBasePath, filename)` where `ConfigBasePath = "config"` (a relative path). No sanitization or validation is applied beyond checking that the field is non-empty (`binding:"required"`). An authenticated attacker can use `../` sequences to read or write files outside the intended `config/` directory, including TLS private keys, OAuth refresh tokens, and any file accessible to the container's UID. Version 0.27.5 fixes the issue.