Lately I've also been seeing Firefox apparently shut down all on it's own. Most times it would happen right after opening up a PDF attachment in our Yahoo webmail email with Adobe DC. I thought that by clearing the cache and history this would fix it. It did not. The only thing that seemed to work was to open up the PDF using a browser instead of Adobe. I also thought that it was an isolated case happening on the office computer. I was using a different computer this morning and it happened on this computer as well. Firefox does not 'crash' and there are no reports to print. I've run it in 'troubleshoot mode' and it does it there as well. Yahoo Email, Adobe Acrobat DC, or Firefox problem?