Multiple security issues in the DBMail driver for the password plugin, including buffer overflows (CVE-2015-2181) and the ability for a remote attacker to execute arbitrary shell commands as root (CVE-2015-2180).
An authenticated user can download arbitrary files from the web server that the web server process has read access to, by uploading a vCard with a specially crafted POST (CVE-2015-5382).
The roundcubemail package has been updated to version 1.0.6, fixing these issues and several other bugs, however the installer is currently known to be broken.