A vulnerability in the file upload functionality of the FlatPress CMS admin panel (version latest) allows an attacker to upload a file with a JavaScript payload disguised as a filename. This can lead to a Cross-Site Scripting (XSS) attack if the uploaded file is accessed by other users. The issue is fixed in version 1.4.dev.
https://huntr.com/bounties/a993a05f-be50-4983-a44a-3bbff1ec00db
https://github.com/flatpressblog/flatpress/commit/f364391085334a7eae02aa2320edd6de7466ec85