(Yes, the referencegroup also should have a target. That indeed is a bib.ietf.org problem.)
$ curl https://bib.ietf.org/public/rfc/bibxml-rfcsubseries/reference.STD.0094.xml
<referencegroup anchor="STD94">
<reference anchor="RFC8949" target="https://www.rfc-editor.org/info/rfc8949">
<front>
<title>Concise Binary Object Representation (CBOR)</title>
<author fullname="C. Bormann" initials="C." surname="Bormann"/>
<author fullname="P. Hoffman" initials="P." surname="Hoffman"/>
<date month="December" year="2020"/>
<abstract>
<t>The Concise Binary Object Representation (CBOR) is a data format whose design goals include the possibility of extremely small code size, fairly small message size, and extensibility without the need for version negotiation. These design goals make it different from earlier binary serializations such as ASN.1 and MessagePack.</t>
<t>This document obsoletes RFC 7049, providing editorial improvements, new details, and errata fixes while keeping full compatibility with the interchange format of RFC 7049. It does not create a new version of the format.</t>
</abstract>
</front>
<seriesInfo name="STD" value="94"/>
<seriesInfo name="RFC" value="8949"/>
<seriesInfo name="DOI" value="10.17487/RFC8949"/>
</reference>
</referencegroup>
Originally posted by @cabo in https://github.com/ietf-tools/xml2rfc/issues/1067#issuecomment-1868277093