Currently listed as firmware R7.50.0.A1.201212171435.SL808x
The list of known issues looks like it is missing stuff.
For example that it’s not possible to configure 8 pin UART yet, or that you can’t exit W32K mode using AT (AAT) on the UART.
Hopefully these issues will be fixed in some new beta firmware soon.
For some reason the latest package update has a different date for the firmware, but it is still the same as listed when checking after installation.
Also, the link to “The upgrade procedure through X-modem” doesn’t lead to any page.