Papra: SSRF via HTTP redirect bypass in webhook delivery

Papra is a minimalistic document management and archiving platform. Prior to version 26.5.0, Papra's webhook delivery system contains an SSRF protection bypass that allows any authenticated organisation member to cause the server to make HTTP requests to internal addresses — loopback, link-local, and RFC-1918 ranges. The SSRF protection validates the registered webhook URL but ignores redirect destinations. The HTTP client (ofetch) follows 3xx responses automatically, and the redirect target is never checked against the blocklist. An attacker registers a webhook pointing to an attacker-controlled server, which redirects incoming POSTs to any internal address. Exploitation was confirmed by live test against the official Docker image. The fix is a single-line change to the webhook HTTP client. This issue has been patched in version 26.5.0.