The W3C XML Signature Syntax and Processing (XMLDsig) specification, starting with 1.0, was originally published with a “RetrievalMethod is a URI … that may be used to obtain key and/or certificate information” statement and no accompanying information about SSRF risks, and this may have contributed to vulnerable implementations such as those discussed in CVE-2023-36661 and CVE-2024-21893. NOTE: this was mitigated in 1.1 and 2.0 via a directly referenced Best Practices document that calls on implementers to be wary of SSRF.