Patched code sample

import mistune
from mistune.plugins import plugin_math

# The CVE describes a vulnerability where content within math blocks ($$...$$)
# was not HTML-escaped, even when the parser was initialized with `escape=True`.
# This example demonstrates the behavior of a *fixed* version of mistune.

# Malicious input that would cause an XSS vulnerability in unpatched versions.
# The payload is inside a math block, which was not being escaped.
malicious_markdown_with_math = "Equation: $$<img src=x onerror=alert('XSS')>$$"

# In a patched version of mistune, creating the parser with `escape=True`
# now correctly applies HTML escaping to the content within math blocks.
# This is the essence of the fix.
safe_parser = mistune.create_markdown(
    escape=True,  # This parameter is now correctly respected by the math plugin.
    plugins=[
        plugin_math,
    ]
)

# When this markdown is parsed by the fixed version, the malicious HTML is sanitized.
safe_html_output = safe_parser(malicious_markdown_with_math)

# The resulting `safe_html_output` will contain the escaped HTML, e.g.:
# '<div class="math">$$<img src=x onerror=alert('XSS')>$$</div>'
# This prevents the browser from interpreting the <img ...> tag and executing
# the malicious script, thus mitigating the vulnerability.
# To verify, you can print the output:
# print(safe_html_output)