SD JWT JS is a JavaScript implementation of the Selective Disclosure JWT (SD-JWT) specification. In version 0.19.0 and earlier, @sd-jwt/decode, also used by @sd-jwt/core, silently drops a tampered Disclosure whose digest no longer matches the Issuer-signed _sd array and returns a reduced claim set, reporting success while the Issuer signature remains valid. Both a tampered Disclosure that remains valid JSON and a Disclosure containing invalid UTF-8 bytes reach this silent-drop behavior. In the latter case, the TextDecoder / Buffer decoding path substitutes U+FFFD replacement characters, recovering syntactically valid disclosure data instead of rejecting the malformed input. This violates RFC 9901 section 7.1 step 5, which requires rejection of unreferenced Disclosures, and section 7.1…