Lxml

The `lxml_html_clean.Cleaner` Python library, and the `lxml.html.clean` module in `lxml`, fails to strip `javascript:`, `vbscript:`, and `data:` URLs from namespaced attributes like `xlink:href` when configured with `safe_attrs_only=False`. This vulnerability, identified as CVE-2026-49825, is a form of stored Cross-Site Scripting (XSS) that allows malicious JavaScript to bypass sanitization, enabling client-side code execution if an application processes and renders untrusted HTML containing such payloads.

lxml versions before 6.1.0 are vulnerable to XML External Entity (XXE) attacks when using iterparse() or ETCompatXMLParser() with default settings, potentially allowing local file reads.