There were two vulnerability found in the PhpMailer library that we use within Admidio. As we understand this bug Admidio should not be affected because we check all Emails for a valid syntax and only those emails are used by the PhpMailer library to send mail. But for security reasons have we updated the library and deliver an Admidio version with this fixed library.
There are also some other bugfixes within this release. You will find the full change list in our issue tracker.
We recommend you to read our announcements for version 3.1 if you have not done before.