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Following a Firefox refresh, I get a warning message about potential security threats for every web page I try to open.

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I went through a Firefox refresh, and now I can't access any websites (including Mozilla), due to potential security threats. One message I get is that "This issue is caused by Qustodio Protection CA, which is either software on your computer or your network." However, I do not have this software on my computer. I never had problems with the program before the refresh.

I went through a Firefox refresh, and now I can't access any websites (including Mozilla), due to potential security threats. One message I get is that "This issue is caused by Qustodio Protection CA, which is either software on your computer or your network." However, I do not have this software on my computer. I never had problems with the program before the refresh.

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Hi JFR34, sorry for the hassle. This usually means there is a "man in the middle" generating fake website certificate, and Firefox not yet set up to trust them. The intermediary could be your security software -- such as Avast, AVG, Bitdefender, ESET, or Kaspersky -- or it might be something or someone untrustworthy.

On the error page, do you find an "Advanced" button? If so, and you click it, there should a ERROR_CODE_IN_CAPS that you can check against the following article:

How to troubleshoot security error codes on secure websites

Let us know whether you can track down the culprit. If not, we'll have more suggestions.

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Thank you, jscher2000. The error message is the following: MOZILLA_PKIX_ERROR_MITM_DETECTED but I am not running any antivirus software. If it helps, I am running a Mac with OS X El Capitan. Is it significant that this happened after the Firefox refresh?

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Hi JFR34, a Firefox refresh removes the old accumulated certificates and gives you a fresh start.

Could you click the View Certificate button on the error page for this site. I'm not sure whether you will see a textual encoded version of the certificate (looks like gibberish) or a dialog that should be similar to the attached but likely have a different "Issued by" section.

If you get the gibberish, you can copy/paste it into a reply for decoding.

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It says the certificate is issued by Qustodio Protection CA, from Qustodio LLC. Qustodio is a program I used for a little while for monitoring my kids' phone activity many years ago. I would happily clear it off my computer if I could find it. I checked spotlight for where it might reside on my hard drive, but it only seems to exist in previous email messages.

This is the SHA-256 fingerprint (whatever that means) that's listed on the certificate: C3:00:BA:28:1A:7D:30:3B:FA:35:F5:4D:35:1E:5C:38:62:8B:AF:9D:B7:01:37:94:35:EC:B5:53:40:75:BF:A9 and this is the SHA1 fingerprint: 11:26:9F:83:56:B6:10:CB:52:2D:5E:E6:73:02:C6:64:36:01:AC:75

Thank you so much!

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Does the method in this article help:

https://www.qustodio.com/en/help/article/1796576/

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This looks promising, and I am taking steps to uninstall the program. Unfortunately, the uninstallation requires my account and login information, which I can't remember since it's been so long. I have contacted the company to see if there is any way around it, but that may take a few days.

Thank you!

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I was able to find my login, and the process worked!!! Thank you so much. This is a great relief.

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JFR34 said

I was able to find my login, and the process worked!!! Thank you so much. This is a great relief.

Hello JFR34,

You inadvertently marked your own post as Chosen Solution; you can rectify it by clicking on the "Undo" button to the right and then mark jscher2000's post as Chosen Solution.

Thank you in advance  !