Hi, Uninstall Firefox from your computer should help.

If your question is resolved by this or another answer, please take a minute to let us know. Thank you.

Thanks. This enabled me to start Firefox from scratch. Unfortunately, I still have the same problem when trying to log into my bank. "The page you are trying to view cannot be shown because the authenticity of the received data could not be verified." I can log in using Internet Explorer and into other secure sites (credit cards and another bank). I can log in using Firefox on another computer. This fault only occurs with one bank and only on this computer with Firefox.

What is the bank URL you're trying to access?

my.if.com (intelligent finance)

See https://www.ssllabs.com/ssltest/analyze.html?d=my.if.com&s=195.171.220.120

This server uses SSL 3, which is obsolete and insecure. Also it does not negotiate TLS 1.0 or 1.1 cipher suites, even though it would support them. You should talk to your bank and ask them, why they use such an insecure server for their online banking. Other modern browsers seem to have the same problem. You may try with older versions of IE, e.g. IE10, but keep in mind, SSL isn't considered secure anymore.

https://developer.mozilla.org/en-US/Firefox/Releases/34/Site_Compatibility#Security https://blog.mozilla.org/security/2014/10/14/the-poodle-attack-and-the-end-of-ssl-3-0/

I don't think that's the problem because it works fine with IE11 and the latest Firefox on a different computer.

Do you get a cert for my.if.com on the other computer?

I do when using IE11. (issued by verisign class 3) but not when using Firefox

The problem has just changed. My laptop just did a Firefox security update and I cant log in to IF on that either now. It must be something to do with the latest security update. IE11 still works fine.

The website may try to fallback to TLS 1.0 in a way that is no longer allowed in current releases or may be using a deprecated cipher suite.

• TLSv1
• TLS_RSA_WITH_RC4_128_MD5

You can open the about:config page via the location/address bar and use its search bar to locate this pref:

• security.tls.insecure_fallback_hosts

You can double-click the line to modify the pref and add the full domain (my.if.com) to this pref. If there are already websites (domains) in this list then add a comma and the new domain (no spaces). You should only see domains separated by a comma in the value column.

If this helps then you can contact this website and ask them to look into this.

• https://developer.mozilla.org/en-US/Firefox/Releases/36/Site_Compatibility#Security
• https://developer.mozilla.org/en-US/Firefox/Releases/37/Site_Compatibility#Security

I don't think that's the problem because it works fine with IE11 ...

IE11 does negotiate a cipher using RC4, whereas Firefox apparently doesn't. https://developer.mozilla.org/en-US/Firefox/Releases/36/Site_Compatibility#Security

... and the latest Firefox on a different computer.

My laptop just did a Firefox security update

As opposed to your previous statement, you did not seem to have the latest Firefox.

IE11 still works fine.

But it is considered insecure. You can check browser capabilities yourself. https://www.ssllabs.com/ssltest/viewMyClient.html

I'd start looking for a new bank, at least for online banking.

Thanks for your help, christ1, and apologies - I clearly did not have the latest Firefox until now. Thanks cor-el. That worked. I am not a security expert. Are we saying Firefox was insecure until this latest update? Is my online bank not keeping up to date with security?

Yes, your online bank is not keeping up to date with security.

Firefox (Mozilla) is usually well ahead of other browsers when it comes to implementing the latest security conceptions.

RFC 7465 - Prohibiting RC4 Cipher Suites: https://tools.ietf.org/html/rfc7465

See also RC4 weaknesses:

• https://wiki.mozilla.org/Security/Server_Side_TLS#Attacks_on_SSL_and_TLS