OpenSIPS 1.5.3 is a minor release of 1.5 branch. This release contains only bug fixing (additional to 1.5.2) - no functionality, scripting or interfacing was changed.
OpenSIPS 1.5.3 contains important fixed related to transaction, dialog and presence support - it is recommended to upgrade, as it provides important stability improvements - OpenSIPS 1.5.3 is now available for download on project web site and SF download system.
The full Changelog is available here.
To get the OpenSIPS 1.5.3 version, see the Downloads page.