Twenty is an open source CRM. In 1.18.0 and earlier, the file serving endpoints in Twenty CRM at /files/* and /file/:fileFolder/:id serve uploaded files using fileStream.pipe(res) without setting any Content-Type, Content-Disposition, or X-Content-Type-Options response headers. This allows an authenticated attacker to upload an HTML file containing JavaScript, which will be rendered by the victim's browser in the context of the Twenty CRM domain when accessed — enabling session hijacking, account takeover, and data theft.