Here is the background information so you know a bit about this ongoing troubleshooting project: Frequent Crashes - Follow-up Eve Jul 23, 2020, 2:45:58 AM It sounds like a double-whammy of a Firefox issue and then an additional Windows issue where you can't run accessibility settings in Windows Safe Mode? Looking into the bug that this is potentially attached to I found this information ( https://bugzilla.mozilla.org/show_bug.cgi?id=1652912 ) : Having NS_FaultTolerantHeap::APIHook_RtlFreeHeap in the crashing stack means Fault Tolerant Heap (= FTH) has been enabled for firefox.exe. FTH is automatically activated when Windows OS detects some heap-related issue which it thinks can be mitigated by FTH such as double free. This crash means Firefox crashed due to some heap related issue earlier, which enabled FTH, but probably FTH was not be able to mitigate the heap issue. First of all, can you check FTH is activated for firefox.exe through event viewer? 1. Open Event Viewer from Start menu (or, run eventvwr from command prompt) 2. In the left pane of Event Viewer, go to Applications and Services Logs > Microsoft > Windows > Fault-Tolerant-Heap > Operational 3. If FTH is activated for firefox.exe, you'll find Event ID 1003 as the attached screenshot. If FTH is activated, instead of looking into this crash, we need to investigate the original heap issue without FTH. You can disable FTH by stopping Diagnostic Policy Service. Can you do the following steps to send us a crash report without FTH? 1. Open Command prompt as Administrator 2. Run "net stop dps" 3. Open Firefox and follow the steps causing the tab crash 4. Send a crash report 5. Go back to the command prompt and run "net start dps" to re-enable the service This may be caused by a third-party application. Given that 99.26% of the crashes of this signature involves AccessibleHandler.dll, do you use a screen reader or some accessibility related application? If it is related to a screen reader, you may have to use Chrome for the time being until you can get more assistance :( You gave me this instruction: 2. In the left pane of Event Viewer, go to Applications and Services Logs > Microsoft > Windows > Fault-Tolerant-Heap > Operational Two issues I had: On a screen reader, I have no idea which is "left column" and "right column" since to a large extent a screen reader is rather "divorced" from the physical layout that sighted people see on the screen (I am totally blind and don't even have a monitor nor mouse running on this machine). Then, I found application and services log... but I did not find anywhere Microsoft > Windows > Fault-Tolerant-Heap > Operational I had Microsoft > and several things with Windows but nothing about fault tolerance. When I went on to your second request: 1. Open Command prompt as Administrator 2. Run "net stop dps" 3. Open Firefox and follow the steps causing the tab crash 4. Send a crash report 5. Go back to the command prompt and run "net start dps" to re-enable the service When I did step 2 as Administrator as you asked, I got the error message that Windows cannot find "net stop dps . I tried the command both with and without the quotation marks and got the same error message. Please remember that the Windows 10 on my computer is the HOME version, not the Windows PROFESSIONAL VERSION with all the security stuff found on that version and used in office environments. From a practical standpoint, unless you folk have another suggestion, it appears that i will likely have to GIVE UP ON FIREFOX (remembering from your message that most of these particular crashes result from an issue with Firefox working with screen readers) until a time comes when Firefox might be updated to resolve issues between Firefox and screen readers. I believe I will contact Vispero, the publisher of JAWS, to let them know about the problem I am having with all these crashes in the current version of Firefox. Of course, I am open to try any other suggestions to further diagnose the problem, if I can carry them out with speech and NO SIGHTED HELP.