Linkwarden is a self-hosted, open-source collaborative bookmark manager to collect, organize and archive webpages. Prior to version 2.13.0, a Server-Side Request Forgery (SSRF) vulnerability in the fetchTitleAndHeaders function allows authenticated users to make arbitrary HTTP requests to internal services due to insufficient URL validation that only checks for "http://" or "https://" prefixes. This issue has been patched in version 2.13.0.