Komunitné fórum Firefox

I am unable to access my usual sites such as @creates or Civil service.Gov.UK or Civil Service Jobs - GOV.UK I am getting this message when I attempt to:

Firefox detected a potential security threat and did not continue to atcreates.com. If you visit this site, attackers could try to steal information like your passwords, emails, or credit card details.

"civilservicejobs.service.gov.uk has a security policy called HTTP Strict Transport Security (HSTS), which means that Firefox can only connect to it securely. You can’t add an exception to visit this site. The issue is most likely with the web site, and there is nothing you can do to resolve it."

Advance provides: Someone could be trying to impersonate the site and you should not continue.

Web sites prove their identity via certificates. Firefox does not trust civilservicejobs.service.gov.uk because its certificate issuer is unknown, the certificate is self-signed, or the server is not sending the correct intermediate certificates.

Error code: SEC_ERROR_UNKNOWN_ISSUER

View Certificate

These are ligit websites that I need for work. Heeeelp!

I keep getting a messages anytime I try to visit a site which I have been to before? here's an example

"mail.aol.com has a security policy called HTTP Strict Transport Security (HSTS), which means that Firefox can only connect to it securely. You can’t add an exception to visit this site."

In the last few months, FireFox (accesed from Roamnia, on Firefox an a MacOS 26, both always updated to the latest available final version) has been showing the error: “Be careful. Something doesn’t look right. Firefox spotted a potentially serious security issue with e360.yale.edu. Someone pretending to be the site could try to steal things like credit card info, passwords, or emails. Advanced What makes the site look dangerous? Sites use certificates issued by a certificate authority to prove they’re really who they say they are. Firefox doesn’t trust this site because it looks like the certificate expired on 14/08/2026. What can you do about it? Your device’s clock is set to 22/09/2026. If this is correct, the security issue is probably with the site itself. If it’s wrong, you can change it in your device’s system settings. View the site’s certificate Learn more about troubleshooting time-related errors Error Code: SEC_ERROR_EXPIRED_CERTIFICATE 22 Sept 2026 08:34:11 EEST“ On perfectly innocent sites. Two examples: FAIR.org does not load beyond the initial “Home” page; e360.yale.edu/ shows the warning instead of accessing the homepage. This is annying, possibly wrong and, as any false security warning, potentially dangerous. Please help.

I'm reposting a question already opened here because a moderator suggested to do so. Actually I though I was posting to the international forum from the URL...

I was trying to access a local HTTPS website of an embedded device (a Siemens S7-1500 PLC) that is using a self-signed certificate, but was unable to go on (attached image #1, in Italian language) due to the the SEC_ERROR_REUSED_ISSUER_AND_SERIAL error. I've browsed a similar PLC webserver in the past, so the fact that the device exposes a similar certificate serial number is not so strange for me, considering also it's self-signed.

The problem is that I cannot follow the instructions of the Mozilla knowledgebase here because I'm not able to identify the correct certificate of the website!

In the attached image #2 you can see that the connection is detected as not encrypted, I suppose because only the form part of the HTML that is posting the data using HTTPS while the rest is using HTTP, but I'm not sure. If I click on the padlock icon (attached image #3) the info about the current certificate is not displayed.

Then I went into Tools > Options and searched for "certificates"; as you can see in the attached images #4 and #5, neither in the Servers tab nor in the Authorities tab I can find any item that is related to 192.168.10.2 (the webserver IP address) or Siemens (the embedded device manufacturer). But unfortunately the error persist! Initially there was a 192.168.10.2:443 line in the Servers tab and I removed it and restarted Firefox, but it didn't solve, so at the moment the situation is the one depicted by the attachments.

I had to use Microsoft Edge to access the website, but I would like to solve this issue and use Firefox instead. Is there anything else I can do to bypass the error? Why doesn't the error page provide a way to correctly identify the wrong certificate using its fingerprint and/or name? Or, maybe, is there a way to disable this check for local IP addresses or for items in a whitelist?

Thanks for your help.

I am continually getting this error message,I can't get rid of this and I'm about to ghange browsers. Secure Connection Failed The page you are trying to view cannot be shown because the authenticity of the received data could not be verified. What can you do about it? The issue is most likely with the website, and there is nothing you can do to resolve it. You can notify the website’s administrator about the problem. Error Code: PR_END_OF_FILE_ERROR

https://www.optimist.com/ip

Peer’s Certificate issuer is not recognized.

HTTP Strict Transport Security: false HTTP Public Key Pinning: false

Certificate chain:

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I've never had Secure Connection Failed warnings before, but now I am getting them often. I don't want to stop using Firefox, but it seems I can get to these sites via other browsers.

Google stopped working for me in Firefox a couple of weeks ago. Every time I enter something in the Google search bar, I get the following error message:

An error occurred during a connection to misho.sodirant.com. SSL received a record that exceeded the maximum permissible length.

How can I fix this? I have had to switch to Chrome to Google anything. I want to stay with Firefox since all my bookmarks are there.

David Beaverton OR

I get several message that: I cannot connect to Amazon, Several websites, etc. It sometimes has something to do with private windows and/or can't connect! Could be license, ssl, etc. When I force a firefox private window, it works for a while then goes back to the same thing. Any ideas how I can fix this?

Доброго времени суток.

Я установил сертификаты по инструкции, которая лежит на s.sber.ru/70VQ2B . После этого не прогружается полностью окно входа на online.sberbank.ru (не видно содержимого фреймов). Проблема полностью аналогична описанной здесь: https://support.mozilla.org/ru/questions/1597415

Firefox ESR115.40 (64-разрядный, Windows 7) - страница выглядит, как на скриншоте по ссылке выше.

Установлены скачанные сертификаты в самом браузере, они отображаются в разделе Управление сертификатами -> Центры сертификации. После этого абсолютно ничего не изменилось.

Может, надо еще что-то сделать? Или на Firefox ESR115.40 вообще работать не будет? До перехода на сертификат от Минцифры России проблем не было.

There is seriously something wrong with the way Firefox operates. There is nothing wrong with the following site so why am I seeing this message?

Be careful. Something doesn’t look right.

Firefox spotted a potentially serious security issue with news.sky.com. Someone pretending to be the site could try to steal things like credit card info, passwords, or emails.

news.sky.com has a security policy called HTTP Strict Transport Security (HSTS), which means that Firefox can only connect to it securely. You can’t add an exception to visit this site. Advanced What makes the site look dangerous?

The site is set up to allow only secure connections, but there’s a problem with the site’s certificate. It’s possible that a bad actor is trying to impersonate the site. Sites use certificates issued by a certificate authority to prove they’re really who they say they are. Firefox doesn’t trust this site because its certificate isn’t valid for news.sky.com. The certificate is only valid for: . What can you do about it?

news.sky.com has a security policy called HTTP Strict Transport Security (HSTS), which means that Firefox can only connect to it securely. You can’t add an exception to visit this site.

Secure Connection Failed

An error occurred during a connection to my.amarkets.org. SSL received a record that exceeded the maximum permissible length. Advanced What makes the site look dangerous?

The page you are trying to view cannot be shown because the authenticity of the received data could not be verified. What can you do about it?

Please contact the website owners to inform them of this problem.

Learn more about secure connection failures

Error Code: SSL_ERROR_RX_RECORD_TOO_LONG

I have started receiving a secure connection failed error message for a portal log-in website that worked fine for the past 6-7 months (see attached document). Other people in my group use Firefox and Bitdefender to access the portal and none of them are having this issue.

I originally believed the problem to be my anti-virus (Bitdefender) and worked with them to resolve the problems. After trying various solutions including clearing my cache, using private mode and turning off different components of their software, Bitdefender believes the problem is with my browser setting and not their software. I also tried accessing the portal using Chrome in both regular and incognito modes and cannot access the site which would seem to rule out the problem being a Firefox browser problem but contacting Firefox support seems to be the next logical step.

I have been to the Firefox FAQ and saw similar problems with potential solutions - DNS over HTTPS, TLSKEYLOGGING issues, add-on exceptions - none of which worked. I have the most recent version of Firefox and am running Windows 11 home version.

Sometimes if I hit refresh after receiving the error message, the browser will try to connect and I will get a server time out message. If I keep hitting "try again", sometimes the portal log-in screen will appear and allow me to log-in. The key word is "sometimes" since often I just keep getting the server time out message.

Any ideas for me to try from this forum?