virtualbox.org

As of VirtualBox 4.3.26, I am no longer being prompted to update VirtualBox. If I manually select Check for Updates... from the Help menu, I am informed that I am already running the most recent version of VirtualBox. However, when I check the Downloads page, there are newer versions available. Why is VirutalBox not updating anymore? Did the developers forget to post the latest version to the application's update U-R-L?

Apparently I'm not the only one experiencing this issue.

It is a known bug and you'll need to update manually to the latest version. I believe this is fixed in 4.3.30 for sure, maybe 4.3.28.