YesWiki has Unauthenticated Server-Side Request Forgery via ActivityPub `Signature.keyId`

Summary The POST /api/forms/formId/actor/inbox route - exposed publicly with acl:"public" - accepts an HTTP Signature header whose keyId parameter is a URL. HttpSignatureService::verifySignature parses the header and immediately makes a server-side HTTP GET to that URL, before any cryptographic...