Firefox 59 can't open Adobe Acrobat Reader Properly

[Franpa]

I go to the options in Firefox and associate PDF files with Adobe Acrobat Reader DC, instead of having them previewed within Firefox. I then click a PDF URL.

Firefox 59 is opening Adobe Acrobat in a broken state, resulting in a process for the program being created but no window or anything. Subsequent attempts to open Adobe Acrobat (even not via Firefox) while this bugged process is present results in more bugged processes being created but still no window.

If you use Task Manager to close all the processes and then run Adobe Acrobat Reader from the Start Menu shortcut, EXE file or some such and not via Firefox, it will open without issue.

Windows 10, build 1803. Adobe Acrobat Reader was reinstalled & updated during my attempts to identify the issue.

[Brummelchen]

changing sandbox level might help
security.sandbox.content.level
(lower = less security)

[Franpa]

Yes, lowering that to a value of 3 seems to resolve the issue.

For anyone else, good information is available here on what the setting does (though I don't understand it all that well myself): https://wiki.mozilla.org/Security/Sandbox

[katoda]

Strange, I have all default (sandbox level 4) and no problems with Adobe Reader DC at all - but I'm using Windows 10 1709., maybe your issue is linked with your version - Insider Preview, I suppose?

[Brummelchen]

1803 is ready and released, in waves.

[Franpa]

I had "Virtualization Support" disabled in the BIOS, apparently Windows uses this functionality to harden O/S security and the BIOS option being disabled may also have negatively affected Firefox's security system in some subtle ways. Note the BIOS option isn't the same as VT-d, VT-x etc. Although I have now re-enabled the Virtualization Support BIOS option (now that I've isolated the Windows 10 1803 Bootup bug to the VT-d option), I haven't re-tested Firefox's ability to launch Adobe Acrobat Reader with Firefox security set to level 4.

I'll test it now though.

Edit: Regardless of BIOS and Firefox security settings, Firefox 60 can open Adobe Acrobat correctly. I don't know if this is because of Firefox being updated, Windows being updated or Adobe Acrobat Reader being updated >.>"

I noticed something interesting, on my dads computer about:support says Sandbox Security is at Level 5 while about:config says the configured value is 4. On my computer both places are at a value of 4. My dad has a Intel 4000 series CPU while I have a first generation Intel i7 920 (D0 stepping) CPU so maybe Firefox is using some security features his CPU supports and mine doesn't.

[Brummelchen]

level is 5 here (v60), still not documented here
https://wiki.mozilla.org/Security/Sandbox
but it explains it well as you found out.

running firefox in sandboxie (!) needs level 3 currently (otherwise no audio)