Halo is an open source website building tool. Prior to version 2.20.13, a vulnerability in Halo allows attackers to bypass file type validation controls. This bypass enables the upload of malicious files including executables and HTML files, which can lead to stored cross-site scripting attacks and potential remote code execution under certain circumstances. This issue has been patched in version 2.20.13.
The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.