AIKIDO-2024-10086

TL;DR

The xmlattr filter in affected versions of Jinja accepts keys containing non-attribute characters. XML/HTML attributes cannot contain spaces, /, >, or =, as each would be interpreted as starting a separate attribute. If an application accepts keys (instead of just values) as user input and renders them in pages visible to other users, an attacker could exploit this to inject additional attributes and perform Cross-site Scripting (XSS).