Hi sz_girl, sorry to hear about the crashes and thank you for the report IDs.

I can't tell what is causing these startup crashes, and it seems to be a very new problem, without other user reports on file on the crash stats server.

If you have not already, please try shutting down and restarting Windows to see whether that helps.

Also, this crash occurs in the JavaScript compiler, so you may be able to avoid the crashes by running Firefox in its Safe Mode. In its Safe Mode, Firefox temporarily bypasses its JavaScript compilers, deactivates extensions, turns off hardware acceleration, and disables some other advanced features to help you assess whether these are causing the problem. Of course you do not want to spend your whole life in Firefox's Safe Mode, but it is worth a test.

If Firefox is not running: Hold down the Shift key when starting Firefox. (On Mac, hold down the option/alt key instead of the Shift key.)

If Firefox is running: You can restart Firefox in Safe Mode using either:

• "3-bar" menu button > "?" Help button > Restart with Add-ons Disabled
• (menu bar) Help menu > Restart with Add-ons Disabled

and OK the restart.

Both scenarios: A small dialog should appear. Click "Start in Safe Mode" (not Refresh).

Any improvement? If you have crashes in Firefox's Safe Mode, please share the new report IDs.

The crashes are about garbage collection (GC; memory cleanup).

• Firefox 63.0.1 Crash Report [@ js::gc::GCRuntime::shouldPreserveJITCode ]

Maybe also do a malware scan.

• https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-caused-malware

Do a malware check with several malware scanning programs on the Windows computer.

• https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-caused-malware

Please scan with all programs because each program detects different malware. All these programs have free versions.

Make sure you update each program to get the latest version of their databases before doing a scan.

• Malwarebytes' Anti-Malware:
  https://www.malwarebytes.com/
• AdwCleaner:
  http://www.bleepingcomputer.com/download/adwcleaner/
  http://www.softpedia.com/get/Antivirus/Removal-Tools/AdwCleaner.shtml
• SuperAntispyware:
  http://www.superantispyware.com/
• Microsoft Safety Scanner:
  https://www.microsoft.com/security/scanner/en-us/default.aspx
• Windows Defender:
  https://windows.microsoft.com/en-us/windows/using-defender
• Spybot Search & Destroy:
  http://www.safer-networking.org/en/index.html
• Kasperky Free Security Scan:
  https://www.kaspersky.com/security-scan

You can also do a check for a rootkit infection with TDSSKiller.

• Anti-rootkit utility TDSSKiller:
  https://support.kaspersky.com/viruses/disinfection/5350

https://support.kaspersky.com/viruses/utility