Vulnerabilities

Python-Markdown version 3.8 contain a vulnerability where malformed HTML-like sequences can cause html.parser.HTMLParser to raise an unhandled AssertionError during Markdown parsing. Because Python-Markdown does not catch this exception, any application that processes attacker-controlled Markdown may crash. This enables remote, unauthenticated Denial of Service in web applications, documentation systems, CI/CD pipelines, and any service that renders untrusted Markdown. The issue was acknowledged by the vendor and fixed in version 3.8.1. This issue causes a remote Denial of Service in any application parsing untrusted Markdown, and can lead to Information Disclosure through uncaught exceptions.

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.

An issue was discovered in markdown2 (aka python-markdown2) through 2.3.5. The safe_mode feature, which is supposed to sanitize user input against XSS, is flawed and does not escape the input properly. With a crafted payload, XSS can be triggered, as demonstrated by omitting the final '>' character from an IMG tag.