Besides fixing some minor bugs and flaws, a major bug regarding $bjs was also fixed. For details see the roadmap archive.

Updating is strongly recommended.

• Upgrade from 1.5 to 1.5.7 (follow the upgrade instructions)
• Upgrade from 1.5.4 to 1.5.7 
  Upload the new files in the cmsimplexh folder over your existing 1.5.4/1.5.5/1.5.6 installation, and change the setting of "autoload" in the configuration of the jQuery Plugin. As always we recommend making a backup of your website before upgrading.