program/steps/addressbook/photo.inc in Roundcube Webmail before 1.0.6 and 1.1.x before 1.1.2 allows remote authenticated users to read arbitrary files via the _alt parameter when uploading a vCard.
https://roundcube.net/news/2015/06/05/updates-1.1.2-and-1.0.6-released
https://github.com/roundcube/roundcubemail/issues/4817
https://github.com/roundcube/roundcubemail/commit/e84fafcec22e7b460db03248dc23ed6b053b15c9
https://github.com/roundcube/roundcubemail/commit/6ccd4c54bcc4cb77365defabe8bbe7d10b2620d4