Threats affecting pkg:pypi/prefab-ui

PrefabHQ prefab-ui versions 0.14.0 through 0.20.2 contain a critical protection mechanism failure in their Generative UI sandbox. The sandbox runs caller-supplied Python code inside Pyodide within a Deno subprocess but starts Deno with unrestricted read, write, and network permissions. This allows an attacker supplying code to read and write files as the server OS user and persist code execution by writing files into the server's virtual environment. The vulnerability is fixed in version 0.21.0 by revoking these permissions before accepting code and restricting network access.