python-markdown2 through 2.3.8 allows XSS because element names are mishandled unless a \w+ match succeeds. For example, an attack might use elementname@ or elementname- with an onclick attribute.
lists.opensuse.org/opensuse-security-announce/2020-05/msg00031.html
lists.opensuse.org/opensuse-security-announce/2020-05/msg00035.html
github.com/trentm/python-markdown2
github.com/trentm/python-markdown2/issues/348
lists.fedoraproject.org/archives/list/[email protected]/message/6XOAIRJJCZNJUALXDHSIGH5PS2H63A3J
lists.fedoraproject.org/archives/list/[email protected]/message/AQLRBGRVRRZK7P5SFL2MNGXFX37YHJAV
lists.fedoraproject.org/archives/list/[email protected]/message/PN6QSHRFZXRQAYZJQ4MOW5MKIXBYOMED
nvd.nist.gov/vuln/detail/CVE-2020-11888