CVE-2026-52767 YesWiki: Unauthenticated ActivityPub Signature-Verification Bypass via `!openssl_verify(...)` accepting `int(-1)`

YesWiki is a wiki system written in PHP. From version 4.6.2 to before version 4.6.6, HttpSignatureService::verifySignature checks the result of PHP's opensslverify with a loose boolean negation - if !opensslverify... throw ... . PHP's opensslverify has four possible return values: 1, 0, -1, and...