The CUBA REST API add-on performs operations on data and entities. Prior to version 7.2.7, the input parameter, which consists of a file path and name, can be manipulated to return the Content-Type header with text/html if the name part ends with .html. This could allow malicious JavaScript code to be executed in the browser. For a successful attack, a malicious file needs to be uploaded beforehand. This issue has been patched in version 7.2.7. A workaround is provided on the Jmix documentation website.

XSS in the /files Endpoint of the Generic REST API