I had this problem about crashing of my browser whenever I use Yahoo Mail. At first I thought it was a virus so I scanned my PC but unfortunately, my AV did not find any infection.
After weeks of searching for a solution, an Advisor in Bleeping Computer directed me to an article posted by Firefox. After following the instructions in the said post, I finally solved the problem that's been bugging me for sol long.
Here's the link to that post of Firefox:
2 years ago