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Error connecting

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Good afternoon, around 1:30 pm central, started getting an error message: Software is preventing Firefox from safely connecting to this site. “Most likely caused by the software “Jupiter “. ( Doesn’t allow any exception to move forward) Took a screenshot of the security padlock information.... can’t upload to this site. But clicking on the padlock reveals Gupreet Walia verified the Firefox certificate expired January 30th, 2013. Don’t know anything about him or any software named Jupiter

Good afternoon, around 1:30 pm central, started getting an error message: Software is preventing Firefox from safely connecting to this site. “Most likely caused by the software “Jupiter “. ( Doesn’t allow any exception to move forward) Took a screenshot of the security padlock information.... can’t upload to this site. But clicking on the padlock reveals Gupreet Walia verified the Firefox certificate expired January 30th, 2013. Don’t know anything about him or any software named Jupiter

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Also, my Firefox version is 88

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This is an unusual message. If the error page has an Advanced button, it may have a View Certificate link. If so, click that. Does the Issued by or Issuer section of the certificate mention Jupiter?

You can check whether the certificate Firefox is getting from the server (or a man in the middle) matches the actual site certificate using a third party certificate test page such as:

https://www.ssllabs.com/ssltest/

Do they match?

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The certificate is so long, I can’t type it all into my phone. Can’t use the internet at all on the Mac

I also see this message on the advanced page. Advanced gives the Error code: MOZZILLA_PKIX_ERROR_MITM_DETECTED

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Oh sorry, don't type the certificate into the SSLLabs page, just the website address.

"MITM" stands for "man in the middle" so it is worth investigating further to see whether this is some kind of spyware.

Does Safari still work? If Safari isn't working either, hmm, does a Mac have a "safe mode" where you can start up without other programs launching automatically?

Is your phone using the same router as your Mac, or is your phone using data on a mobile network? If everything using the household network as a problem, sometimes the router needs to be rebooted/"power cycled".