Maybe this should require a new thread but shouldn't this fix also be available for 600/1100 devices? I understand they're end of support but they should still get security fixes I believe.
I looked at the R77.20.80 page which is the last version for 600/1100's and the download links to fw1_dep_R77_990172392_20.img from 2018-07-04. But if you search R77.20.80 in the Downloads site you can find build 990172487 from 2019-06-20 which has no documentation and seems to be for 1100's specifically. Also it's a .tgz file instead of a .img which seems weird. Maybe this file is for the aforementioned vulnerability?
If the build I found is the newest and includes a major fix I would think it should be documented, added to the main R77.20.80 page, and should be an img file not a .tgz file.
Edit: I'd also think if this is the newest version it should be what's suggested when logged into the Gaia Embedded web page. I've recently just upgraded 20-30 devices to the suggest version just to see that two hotfixes have come out since that don't show up in documentation or any official way.