"Mozilla has started to distribute two new system add-ons for Firefox 49.0 and Firefox 49.0.1 to address two issues affecting Adobe Flash Player and graphics issues.Source: gHacks Tech News
"The organization is working on Firefox 49.0.2 currently, but made the decision to release two new patches for the current stable version of Firefox as system add-ons to address issues that users are affected by.
"System add-ons are like hotfixes. They can be pushed out to all Firefox users who have automatic updates enabled to fix issues of the browser. That's usually a lot faster than having to create a new build of Firefox.
"The two system add-ons address two issues in Firefox 49 and 50. ..."
Firefox 49: two new system add-ons to fix Flash and graphics issues