GHSA-6J4C-MGQR-QV76 Kirby: Access to image files outside of the site root via path traversal in the media handling

TL;DR This vulnerability affects all Kirby sites that are deployed in a way that their index root on the server is next to a second directory that is read-accessible to PHP and shares the same name prefix such as the site with the index root /var/www/site being next to /var/www/site2. It was...