Sandboxie 5.27.3, 25% CPU With Firefox (Please Fix)

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Moderator: Barb@Invincea

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Sandboxie 5.27.3, 25% CPU With Firefox (Please Fix)

Post by TyeBox » Sun Feb 10, 2019 12:28 pm

Windows 10 Pro 10.0.17763 Build 17763. 65.0 (64-bit). Its been a year or two since users have reported this same issue. I had the same problem in Windows 7. Firefox has been refining their sandboxing, now at a level of "5", above the previous 2 or 3. I read somewhere this enables built in DEP/ALSR and other EMET/MBAE features; this can be applied from outside but surely Firefox has it nailed & probably includes other mitigations.

If FF sandboxing is disabled (set to "0") and the sandboxie folder deleted, Firefox no longer pounds ucrtbase.dll, and there are no more cpu issues. However it does reduce security of the browser, potentially requiring a more routine purge of the sandbox folder in case of infection. It's nice to have layered security that works instead of compromising it, and having ones last pass account hacked/password sniffed or something! Just curious if there is anything you can do to mitigate against this issue, and how serious you think it could be, and if there are other sandboxie based mitigations you might recommend because of that.

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Re: Sandboxie 5.27.3, 25% CPU With Firefox (Please Fix)

Post by Barb@Invincea » Mon Feb 11, 2019 9:59 am

Hi TyeBox,

Please, follow the guidelines so that we can better assist you:

Also include screenshots and details regarding the numbers that you are seeing, and the difference between running FF sandboxed (new sandbox) and non-sandboxed.

Regarding Firefox security, please see these threads: (they are related to a previous issue that is now fixed, but they cover a lot of questions regarding FF sandbox):


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