I have difficulties to log in the Physics Stack Exchange site via the Opera browser. It says:

Your connection is not private This server could not prove that it is physics.stackexchange.com; its security certificate is not valid at this time. This may be caused by a misconfiguration or an attacker intercepting your connection.


When you connect to a secure website, the server hosting that site presents your browser with something called a "certificate" to verify its identity. This certificate contains identity information, such as the address of the website, which is verified by a third party that your computer trusts. By checking that the address in the certificate matches the address of the website, it is possible to verify that you are securely communicating with the website you intended, and not a third party (such as an attacker on your network).

You cannot visit physics.stackexchange.com right now because the website uses HSTS. Network errors and attacks are usually temporary, so this page will probably work later.

How should I do on the Opera browser to fix this issue to log in Physics Stack Exchange site?

  • 2
    $\begingroup$ (1) What version of Opera? Does upgrading your browser to the most current version fix the problem? (2) You should be able to click some links in your error dialog to show some information about the certificate — who it claims as its issuer, its “fingerprint,” perhaps some other useful things. Can you post that data as well? $\endgroup$
    – rob Mod
    Commented Oct 17, 2021 at 20:42
  • 5
    $\begingroup$ ERR_CERT_DATE_INVALID is an error that indicates Opera thinks SE's certificate is expired. Make sure that your computer is set to the correct current date & time. The current certificate is only valid from Mon, 04 Oct 2021 16:19:09 GMT onwards, so if you're living in the past you might have issues... $\endgroup$
    – ACuriousMind Mod
    Commented Oct 17, 2021 at 20:48
  • $\begingroup$ Related: Which browsers are officially supported, and what else do I need? $\endgroup$ Commented Oct 18, 2021 at 14:04


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