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When following a link from a news website I keep getting this message - Secure Connection Failed - The page you are trying to view cannot be shown because the authenticity of the received data could not be verified. It loads on my iPhone and other browsers using the same link. What setting do I need to address to get this to stop?

Why are you closing the baked-in cert expiration support thread two days before it happens? Wouldn't it make a whole ton more sense to leave it open during the actual problem period?

https://support.mozilla.org/en-US/questions/1468274

Over and over again when I try to open a website I get the notice that says "Secure Connection Failed". I have to restart my laptop and then I can open the website that I tried to access before. I've tried using the suggestions in the forum with no result in solving this problem. I've attached the page that comes up showing the problem.

Subject: Persistent “Secure Connection Failed” after SSL certificate was re-issued – cannot clear cached certificate Hello Firefox Support, I am experiencing a persistent SSL certificate problem that only occurs in Firefox. Background

Domain: j3tourshongkong.com (and www.j3tourshongkong.com) The domain was recently moved to a redirect service (redirect.pizza) A new valid SSL certificate was issued by Let’s Encrypt via the redirect service The certificate is confirmed working by the certificate issuer and by redirect.pizza support

Current situation

HTTPS works correctly in Chrome, Edge, Safari, and on mobile browsers HTTPS works correctly on the same computer when using Chrome In Firefox (both normal and Private windows) I continue to receive “Secure Connection Failed / Not Secure”

What I have already tried

Cleared cookies and site data for the domain Cleared all recent history (including cache) Tested in a Private Window Restarted Firefox multiple times

None of these steps resolved the issue in my current Firefox profile. It appears Firefox has cached the previous (invalid) certificate state and is not refreshing it, even though a valid certificate is now being presented by the server. Could you please advise:

Is there a more thorough way to force Firefox to discard a cached SSL certificate for a specific domain? Or is this a known issue that requires a fix on the Firefox side?

I am happy to provide any additional technical details or screenshots if needed. Thank you for your help. Best regards, Jamie Lloyd

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?

I have an website which I prior to this error message have visited many times on Firefox and had no problems. Recently though around two days ago I noticed that I couldn't get in and was met with the following message "Warning: Potential Security Risk Ahead". I can't bypass it apparently and I really need to be able to access this site as it's a University site.

I can access the site on other browsers such as Chrome and Edge but I use Firefox as my default browser and I'd like to keep it that way. I'd appreciate any help I can get.

Said link: https://canvas.gu.se/

Firefox is giving me an error on https://stemgateway.nasa.gov but the site is perfectly accessible using MS Edge and using Firefox on another computer. I uninstalled and reinstalled Firefox, changed the proxy settings to not use a proxy, tested a VPN, and changed DNS servers. Below is a picture of the error and of the certificate which seems to be present in Firefox already.

Hello,

Since this morning, I haven't been able to access Bsky on my laptop because of a supposed HSTS risk, which means I can't add an exception to visit it. I use Firefox on my Android and going to the mobile version of the website lets me in no problem, so I assume there's an issue with my laptop.

I'd usually wait a few days and let it solve itself but just in case it's something on my end, I'd like to solve it! I'm on 151.0.4 (64-bit), don't use a VPN or an anti-virus, I have a couple of privacy add-ons but they've been here forever and they've never caused a fuss. I can post a screenshot of the error code and the certificate it sends me if it's any help.

I'd appreciate any pointers! Thanks!

Have used Firefox for years. Today, went to standard sites (eg weather info, local blog site) and get told they aren't secure and can't be loaded. Have tried re-installing Firefox, clearing cookies but no change. No problem with same sites from Chrome. Message is:

Looks like there’s a problem with this site

www.portlandbirdobs.com sent back an empty page. What can you do about it?

   The site could be temporarily unavailable or too busy. Try again in a few moments.
   If you are unable to load any pages, check your computer’s network connection.
   If your computer or network is protected by a firewall or proxy, make sure that Firefox is permitted to access the web.

Error Code: NS_ERROR_NET_EMPTY_RESPONS

I am getting the below message when trying to log into the EFTPS site. I have never had this issue before.

Did Not Connect: Potential Security Issue

Firefox detected a potential security threat and did not continue to www.eftps.gov because this website requires a secure connection.

What can you do about it?

www.eftps.gov 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 website, and there is nothing you can do to resolve it.

If you are on a corporate network or using antivirus software, you can reach out to the support teams for assistance. You can also notify the website’s administrator about the 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.

As the title says, with both with https and http firefox displays this warning:

https://i.imgur.com/MQLsaCk.png

But no way to bypass it, trying to login to my ubiquiti edgerouter at http://192.168.1.1 or https://192.168.1.1

What can i do?

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.

Untill last night i could conect with that site https://imtw.ru and its sub forums without eny problem . Today when i press the link i recieve a message that the connection is rejected "Failure to secure connection". As you van see it has the https:// infront and i repeat i was able to connect last night. What may be wrong?

I read the The Times in the UK and have no problem viewing on my iPad and Google Pixel phone using the Firefox browser. However on my laptop using Firefox I get a screen that says Secure connection failed and recommends contacting the vendor as there is no workaround. On microsoft Edge there is no problem I like Firefox but for me this is a major limitation. Any ideas or suggestions welcome

At your recommendation I signed up to Ad Avoid and now FireFox tells me that I could/should not access BT.Com because of the certificate issued by Ad Avoid

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.

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 !!!!!!!!