A new crash signature and hovering outside the top 20 at present. Apparently the current suspicion from engineers is that it may be caused by malware.

• Troubleshoot Firefox issues caused by malware

Try with as many of the most up to date malware scanners possible. I have mentioned this thread in the related bug so I suggest you sign up to bugzilla then visit the bug page. By default you will get an option to click on [save changes] and will be cc by email on the bug progress.

• Bug 1175454 - startup crash in RtlpLowFragHeapFree | RtlFreeHeap | HeapFree | nsUrlClassifierPrefixSet::StoreToFd(mozilla::Scoped<T>&)
  • Note https://bugzilla.mozilla.org/page.cgi?id=etiquette.html
    It is usually best to wait to be asked for information, unless you can provide solutions.
  • But you may like to vote for the bug, and CC yourself.

For forum cross referencing purposes

• Your Crash Reports bp-3a708f93-2a6c-4aa9-804f-5d1142150619
  bp-3a708f93-2a6c-4aa9-804f-5d1142150619
  • Crash Signature: RtlpLowFragHeapFree | RtlFreeHeap | HeapFree | nsUrlClassifierPrefixSet::StoreToFd(mozilla::Scoped<T>&)
  • Related Bugs: Bug 1175454
• See also /questions/1067780 & /questions/1067527

Thanks for looking into this so quickly. I'll update this post if the scan return any malware :

• Malware Bytes Free :

     threat scan : nothing

• Malware bytes (Kaseya Anti Malware with license)

    Quick Scan : nothing
    Flash Scan : nothing
    Full Scan : nothing

• SUPERAntiSpyware :

     Critical Point Scan : nothing
     Quick Scan : 40 tracking cookie found and removed
     Full Scan : 2 tracking cookies
     Custom Scan of C:\ : nothing

• Microsoft Safety Scanner :

     Fast Scan : nothing
     Full Scan : nothing

• adwCleaner :

     Scan : nothing

• Kaspersky TDSSKiller :

     Full Scan : no threats

Don't forget to use Anti-rootkit utility TDSSKiller too.

TDSSKiller also found nothing.