Nextcloud Deck is a kanban style organization tool aimed at personal planning and project organization for teams integrated with Nextcloud. Prior to 1.12.7, 1.14.4, and 1.15.1, file extension can be spoofed by using RTLO characters, tricking users into download files with a different extension than what is displayed. This vulnerability is fixed in 1.12.7, 1.14.4, and 1.15.1.
Deck is a kanban style organization tool aimed at personal planning and project organization for teams integrated with Nextcloud. In affected versions users could be tricked into executing malicious code that would execute in their browser via HTML sent as a comment. It is recommended that the Nextcloud Deck is upgraded to version 1.9.5 or 1.11.2. There are no known workarounds for this vulnerability.