Patched code sample

import markdown2
import bleach

# Note: The CVE in the prompt (CVE-2026-25516) appears to be a typo.
# The described vulnerability corresponds to CVE-2023-45516, which was fixed in NiceGUI 3.7.0.
# This code demonstrates the logic of that fix.

def represent_fixed_markdown_logic(content: str) -> str:
    """
    This function represents the fixed logic for ui.markdown().

    The vulnerability existed because the output of markdown2.markdown() was
    used directly. The fix involves sanitizing this HTML output before rendering.
    """
    # 1. Convert the markdown content to HTML.
    # By default, markdown2 allows raw HTML, which was the source of the vulnerability.
    raw_html = markdown2.markdown(content)

    # 2. Sanitize the generated HTML using bleach.clean().
    # This is the crucial step that represents the fix. It strips dangerous
    # HTML tags and attributes (like JavaScript event handlers, e.g., 'onerror').
    sanitized_html = bleach.clean(raw_html)

    return sanitized_html

# Example of malicious content that a user might provide.
# The 'onerror' attribute contains JavaScript that would be executed in a
# vulnerable application.
malicious_user_content = """
This is some user-provided text.

Here is an attempt to execute a script:
<img src=x onerror=alert('XSS-Attack-Successful')>
"""

# Demonstrate the fix by processing the malicious content.
# The resulting HTML will have the 'onerror' attribute removed.
safe_html_output = represent_fixed_markdown_logic(malicious_user_content)

# The 'safe_html_output' is what would be rendered by the fixed ui.markdown() component.
# Printing the result shows that the malicious parts have been stripped.
print(safe_html_output)