A security software update is underway for HTC ChaCha which is pushing out over the air (FOTA). You’ll get prompt when the update is ready for your handset. Just be careful not to cancel because you might not get it.
We dont know whats really changing once updated is installed, but we encourage you to update to the latest version. We are waiting for ThreeUK to release a changelog.
Here is all you need to know on how to check for the latest updates and how to upgrade your phone firmware.