Gogs: Open Redirect via redirect_to in Gogs

Gogs is an open source self-hosted Git service. Prior to 0.14.3, an open redirect vulnerability exists in Gogs where attacker-controlled redirect_to parameters can bypass validation, allowing redirection to arbitrary external sites. All redirects in Gogs that are validated via the IsSameSite function are vulnerable. The function only inspects the first two characters of the URL string. This check fails to account for directory traversal sequences followed by backslashes. This vulnerability is fixed in 0.14.3.