Basic Firefox signing/encryption question

An OASIS TC is currently toying with the idea that Mozilla Firefox can,
without adding any native extension code, perform XML Signatures and
possibly also XML Encryption, by an invocation from a web page: 

http://www.oasis-open.org/committees/download.php/16304/agsc-tpki-requirements-00.txt

To my knowledge the only thing available in a standard distribution is the
"signText()" function.  signText only supports the signing of a plain/text
string (at least if the user is taken in consideration...).  In addition the
signature is limited to PKCS #7.

Could somebody ON THIS LIST (not off-list) verify (or not) this statement?

Anders Rundgren