Fiber is an Express inspired web framework written in Go. Prior to 3.3.0, the default Authorizer function in the BasicAuth middleware in middleware/basicauth/config.go uses short-circuit evaluation that skips password hash comparison for non-existent usernames, enabling reliable remote username enumeration through response timing differences. This issue is fixed in version 3.3.0.
https://github.com/gofiber/fiber/security/advisories/GHSA-g5vh-55hw-rxm8
https://github.com/gofiber/fiber/releases/tag/v3.3.0
https://github.com/gofiber/fiber/pull/4245
https://github.com/gofiber/fiber/commit/c7ac00edd19f9669b1aebbec6e229658baaa059e