OpenCart v1.5.6.1 was released on 7 January 2014 and is mainly a bug fix version.

OpenCart 1.5.6.1 Features, Fixes and Changes
– OpenBay Integration fixes and cleanup.
– PayPal payment modules fixes.
– Admin security fix.
– MySQLI support

Full Github list of changes/commits can be found here…
OpenCart Download: OpenCart v1.5.6.1…