GHSA-X34J-47HF-4XG7 TinaCMS admin preview iframe loads an attacker-controlled origin from the URL fragment

Summary The TinaCMS admin builds its preview from the // hash-router splat without checking that the value stays same-origin. A fragment with a doubled slash ///attacker.example/p becomes the protocol-relative URL //attacker.example/p, so the admin frames an external site. That same unvalidated...