XWiki Platform is a generic wiki platform offering runtime services for applications built on top of it. When uploading an attachment with a malicious filename, malicious JavaScript code could be executed. This requires a social engineering attack to get the victim into uploading a file with a malicious name. The malicious code is solely executed during the upload and affects only the user uploading the attachment. While this allows performing actions in the name of that user, it seems unlikely that a user wouldn't notice the malicious filename while uploading the attachment. This has been patched in XWiki 14.10.21, 15.5.5, 15.10.6 and 16.0.0.