CVE-2021-30560: Nokogiri has vulnerable dependencies on libxml2 and libxslt

The vulnerability CVE-2021-30560 is a use-after-free in the libxslt C library, which Nokogiri uses. The provided commit information shows that Nokogiri addressed this by updating its vendored version of libxslt. There are no code changes in Nokogiri's Ruby source files that indicate a specific vulnerable Ruby function. The vulnerability is in the underlying C library, not in Nokogiri's Ruby code. Therefore, no specific Ruby functions can be identified as 'vulnerable' from the patch; rather, any function in Nokogiri that uses libxslt for XSLT transformations could potentially trigger the vulnerability if processing a malicious XSLT file with a vulnerable version of libxslt.