OpenRun's redirect URL validation attempts to restrict redirects to the same host and scheme as the current website by validating the referrer header. However, if an attacker supplies a redirect URL such as http://127.0.0.1:25222//fushuling.com, the validation passes because the host and scheme match. The final redirect uses the path component, which is //fushuling.com. Browsers interpret URLs starting with // as protocol-relative URLs, causing the redirect to an external domain (http://fushuling.com), thus bypassing the intended restrictions and resulting in an open redirect vulnerability (CWE-601). This behavior was reproducible locally and affects OpenRun versions before 0.17.7.

This vulnerability allows attackers to perform open redirect attacks by bypassing URL validation. Users can be redirected to arbitrary external websites, which can facilitate phishing, social engineering, or other malicious activities. The vulnerability does not require authentication and can be triggered by crafting a specially formed redirect URL. There are no known exploits in the wild at this time.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, users should avoid relying solely on host and scheme validation for redirect URLs and implement stricter validation that properly handles URLs with protocol-relative paths (starting with //).