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I am getting a message that secure connection failed, it is happening for Amazon.com and maybe netflix as I can't log on or access the sites

I just got a Netgear router. Firefox won't let me connect because of the self-certification. I can only get on the internet via my Proton VPN. How can I fix this?

Specifically, I get this message--The certificate is not trusted because it is self-signed.

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.

Using firefox 140.6.0esr on Windows 10 with noScript and uBlock Origin

Infrastructure for my health insurance provider website uses a self-signed certificate. The infra has a different URL from the main page and was initially failing with "CORS failed", which turned out to be the cert issue.

I copied the infra URL from the dev tools network log and opened it directly, and accepted the invalid cert. I can see the new exception in cert_override.txt.

Then, after unblocking the site in uBlock origin, POST and GET requests to the infra URL succeed, but OPTIONS requests are still failing with "CORS failed", and security status "SEC_ERROR_UNKNOWN_ISSUER"

Is there anything else I can do so the OPTIONS request honors the exception in cert_override.txt?

When I enter a company name into search this message appears:

Secure Connection Failed

An error occurred during a connection to vanilla-search.com. SSL received a record that exceeded the maximum permissible length.

Error code: SSL_ERROR_RX_RECORD_TOO_LONG

   The page you are trying to view cannot be shown because the authenticity of the received data could not be verified.
   Please contact the website owners to inform them of this problem.

Learn more…

Ever since the update to iOS 26.4, I’m unable to access insecure or untrusted sites. I first noticed this when trying to get to some devices on my local network, but I tested an insecure site on the internet and it happened there too. What’s weird is that Safari does still let me access these sites after proceeding through the warning as expected (albeit with a refresh which is new, maybe a bug), but Firefox will just load for a split second and stop.

Just a quick rundown of some additional info:

- Firefox has been updated to the latest version, 149.0. - The local sites are ones I’ve previously given trust to - Firefox has local network access enabled in settings - This also occurs on iPadOS 26.4 - I did some more testing while writing this and it seems intermittent? For example, I have a server with several docker containers, and I can access some of them if I put the port in with the IP but others I can’t. I also have a device that I can get to via hostname but not IP. - I also downloaded Chrome to test things there and I get the “this connection isn’t private” message with the option to proceed anyway, and I’m able to access these sites there.

I’m not sure if this is something on Firefox’s end, Apple’s end, or a combination of the two. Either way, I wanted to see if there was anyone else experiencing this issue or if it’s just me.

need to be able to download my old sites. and stop getting error 522 can not connect to some sites due to not secure anymore... help need to watch some movie sites.. Jose

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

This is my website I work on daily - I can normally open it in this browser BUT because Im on my laptop it is flagged as a security risk - and its not - https://passive-income-system.co.uk/

Be careful. Something doesn’t look right.

Firefox spotted a potentially serious security issue with www.aol.fr. Someone pretending to be the site could try to steal things like credit card info, passwords, or emails. ??????? I used Aol since 1998 !!!!!!!!

After the latest update to Firefox for iOS, I can't open pages with an untrusted SSL certificate. It's a blank page. There's no threat prompt that I can accept to proceed (as before). I use Firefox for iOS primarily to log in to Ubiquiti devices on the local network (address: 192.168.x.x). Everything worked fine until recently. Now it doesn't. I cleared the browser cache, disabled security, and that didn't help. I uninstalled and reinstalled the browser, and that didn't help either. Other iOS browsers (e.g., Brave and Safari) work fine—the untrusted certificate prompt appears, and after accepting the threat, the login screen appears. Please help.

Secure Connection Failed

An error occurred during a connection to upl-upm.pushbuttonformula.com. SSL received a record that exceeded the maximum permissible length.

Error code: SSL_ERROR_RX_RECORD_TOO_LONG

Your computer thinks it is May 1, 2026, which prevents Firefox from connecting securely. To visit www.olx.com.br, update your computer clock in your system settings to the current date, time, and time zone, and then refresh www.olx.com.br.

I am trying to access static IP addresses on my Intranet. I could in the past type in the IP address and I would get a notice that the site is not secure and allow me to continue to the site. Now it tells me that the website cannot be reached. I need to get to the GUI interface of cameras on my network. How do I get this to work?

When I try to access the Newsmax website, I get a black screen with the message which says,

"Secure Connection Failed The connection to www.newsmax.com was interrupted while the page was loading.

   The page you are trying to view cannot be shown because the authenticity of the received data could not be verified.
   Please contact the website owners to inform them of this problem." 

I have no problem accessing other sites, so what can I do to get the resolved?

Firefox spotted a potentially serious security issue with westdell.fortiddns.com:40443. Someone pretending to be the site could try to steal things like credit card info, passwords, or emails. Advanced I can't open a lot of sites, I can click on advanced and select to open the site at risk but will not open. I can open these site in Google Chrome or Safari no problem. i follow the article "How to disable the Enterprise Roots preference" and turned both to "False" and still not luck Thanks

Why does my older computer running Windows 7 keep losing the ability to access "https:// sites"?

To resolve, I have to reset the network adapter (sometimes successful) or restart the computer to access these sites.

To be honest. Firefox is starting to be a big pain to use. I'm starting to see more and more of this screen where it say's "Be careful. Something doesn't look right" Even when i go to the advance and say proceed. Nothing happens and i'm getting no where. I know many of the sites don't have anything to do with asking for credit card, Scam or even having popup's. I test the sites in other browsers and there work without any issues. But Firefox is starting to lock me out of many sites due to this. How can i make this stop. As i used Firefox for many years.

The sample that is in the screenshot is a Anime data base that i have also used for years. But today shows this. But was working fine yesteday. What is going on and how can i fix it. So i can start using the browser that i love on the sites i want to.