I checked this issue more precisely. The results are the following: Randomly when downloading a file from my yahoo business mail then closes automatically the tab of yahoo website (So if I have only one tab with the yahoo business mail open then closes the whole Firefox. On the other hand, if I have two or more tabs open then closes only the tab of yahoo business mail). I disabled my add ons of Firefox and turned off my antivirus, but nothing happened and the tab with yahoo business mail still closes automatically. Therefore is it an issue with the yahoo software in business mail, or an issue of Firefox ? For example Chrome doesn't have such issue.

Hello, Please check that you are using the updated version of the Firefox browser. Moreover, also try disabling add ons and firewall protection. Please let me know if it works or not.

I am using 88.0.1 (64 bit) for Windows 10 (with all the last updates). So this is the last version of Firefox. Also, I already disabled all my add ons (which are very few) and turned off my antivirus protection. The problem still persists.