I don't have all the facts on this so please contribute if you have something. There appears to be quite an amount of stress over our present Firefox 52.x ESR. The are upcoming releases of Firefox both the regular editon and the ESR due soon. Part of the problem here involves an increasing number of website operators who either probibit or strongly insist that you be using the latest version of Firefox.
Example:
I am a long time customer of BankofAmerica.com. And for the last year or so every time I go to review my accounts there is a banner across the top of the page warning me that I am not using a certified Browser. This is the case for 52.x.x ESR. I have downloaded, and have transitioned to FF 59.x, the warning is not there.
If you review:
https://wiki.mozilla.org/Release_Management/Calendar
you'll notice that we are just a few weeks away from the release of FF 60 and ESR 52.8; 60.0.
I spent last week at the National Association of Broadcasters Show here in Las Vegas where I visited the Adobe booth and asked a technical person about the status of Flash. His answer was they offer a free "kit" and instructions on how to transition away from Flash to HTML5. He all but said they don't support Flash anymore. Officially Adobe has indicated they will support Flash through the Fall of 2020. I didn't get that feeling from this tech person.
There is at least one report that FF 60.0b13 crashes if Flash 29.0.0.140 is installed. This may be a one off incident, it may really be intentional on Mozillas part.
The Mageia team will continue to test and work to bring you the best version of FF we can. But, IMO, over the next weeks or so that may be a bit of a bumpy road.