Mozilla Developers about from the Firefox codebase user-accessible settings to disable multi-processing (e10s). Fallback to single-process mode is cited as a reason for deprecating support for its low security and potential stability issues due to lack of full coverage in testing. Single process mode is marked as unsuitable for everyday use.
Starting with Firefox 68, about:config will settings "browser.tabs.remote.force-enable" and
"browser.tabs.remote.force-disable" controls enabling e10s. Also, setting the "browser.tabs.remote.autostart" option to "false" will not automatically disable multi-processing on desktop versions of Firefox, in official builds, and on startup without enabling automated test execution mode.
In mobile builds, when running tests (with the MOZ_DISABLE_NONLOCAL_CONNECTIONS environment variable or the "--disable-e10s" option enabled), and in unofficial builds (without MOZ_OFFICIAL), the "browser.tabs.remote.autostart" option can still be used to disable e10s . For developers, a workaround has also been added to disable e10s by setting the "MOZ_FORCE_DISABLE_E10S" environment variable before launching the browser.
Additionally, it can be noted TLS 1.0 and 1.1 deprecation plan in Firefox. In March 2020, the ability to establish a secure connection using TLS 1.0 and 1.1 will be removed and an attempt to open sites that do not support TLS 1.2 or TLS 1.3 will result in an error. Legacy TLS support will be deprecated in October 2019 for nightly builds.
The end of support is coordinated with the developers of other browsers, and the ability to use TLS 1.0 and 1.1 will be dropped in Safari, Firefox, Edge, and Chrome at the same time. Site administrators are encouraged to support at least TLS 1.2, and preferably TLS 1.3. Most sites have already migrated to TLS 1.2, for example, out of a million verified hosts, only 8000 do not support TLS 1.2.
Source: opennet.ru