Stored XSS in "gallery" application (NC-SA-2016-001)

Due to a recent migration of the Gallery app to the new sharing endpoint a parameter changed from an integer to a string value. This value wasn’t sanitized before and was thus now vulnerable to a Cross-Site-Scripting attack.To exploit this vulnerability an authenticated attacker has to share a folder with someone else, get them to open the shared folder in the Gallery app and open the sharing window there. Since Nextcloud employs a strict Content-Security-Policy this vulnerability is only exploitable in browsers not supporting Content-Security-Policy. You can check at caniuse.com whether your browser supports CSP.