Your post was moved from the Update Announcement thread to Support → Software and Applications because your issue had nothing to do with the Update. While we appreciate your enthusiasm, your post was misplaced and off-topic for the Update Announcement topic.
However, this Support topic has hopefully allowed you to learn some valuable troubleshooting skills.
Consider offering some thanks to our Moderation staff for attempting to guide you in the right direction; rather than reacting negatively when the help is offered.
It can make all the difference. 
Please do not refer to an issue as a bug. 
If you do that, you are expected at least to provide a link to a confirmed bug report. As it turns out, your “bug” was simply your failure to apply troubleshooting 101. Mozilla have all kinds of articles to help Firefox (and Thunderbird) issues. I dare say, they should have been your first port of call.
Remember, a bug is not a bug unless an issue can be reproduced – usually by the devs; or, in any case, other people. 
Your resolution speaks for itself. 
Regards.
The following is added in case it’s useful;
Welcome to the Manjaro community
As a new or infrequent forum user, please take some time to familiarise yourself with Forum requirements, and the many ways to use the forum to your benefit:
Update Announcements
The Update Announcements contain important information and a Known Issues and Solutions section that should generally be checked before posting a request for support.
System Information
While information from *-fetch type apps might be fine for someone wishing to buy your computer, for Support purposes more indepth information is usually needed;
It’s best to ask your system directly. 
Output of the inxi command with appropriate parameters will achieve this (naturally, formatted according to forum requirements) and will generally be more useful for those wishing to help:
inxi --filter --verbosity=8
or the short form:
inxi -zv8
- inxi man pages (Arch Manual)
Be prepared to provide more information and outputs from other commands whenever asked. It’s equally important to provide as much actionable information as possible in your first post, rather than simply indicating there is a problem.