There is security software like Avast, Kaspersky, BitDefender and ESET that intercept secure connection certificates and send their own.

https://support.mozilla.org/en-US/kb/firefox-cant-load-websites-other-browsers-can

https://support.mozilla.org/en-US/kb/firefox-and-other-browsers-cant-load-websites

https://support.mozilla.org/en-US/kb/secure-connection-failed-error-message

https://support.mozilla.org/en-US/kb/connection-untrusted-error-message

Websites don't load - troubleshoot and fix error messages

http://kb.mozillazine.org/Error_loading_websites

Yes, I was aware of that. I have tried disabling HTTPS scanning in Avast, adding an exception for the website, even temporarily disabling the Web Shield completely, but the problem persists.

And it only occurs for Firefox 63; Firefox 62 and below, IE, Chrome, Opera, Palemoon, and Vivaldi all display the websites just fine. Are they all that much less secure than Firefox 63?

(I also see that the CSS and scripts for https://support.mozilla.org are not being loaded, though the HTML is displayed; could this be related?)

This error indicates that the server initiates a HTTP/2 connection, but Firefox detects an invalid TLS configuration in the server response. This is likely not an issue with the certificate, but this is a problem with the server setup and there are invalid cipher suites for HTTP/2 claimed (INADEQUATE_SECURITY).

This shouldn't happen with Mozilla websites.

You can check the connection settings.

• Options/Preferences -> General -> Network: Connection -> Settings

If you do not need to use a proxy to connect to internet then try to select "No Proxy" if "Use the system proxy settings" or one of the others do not work properly.

See "Firefox connection settings":

• https://support.mozilla.org/en-US/kb/firefox-cant-load-websites-other-browsers-can

I tried all the proxy settings (none, auto-detect, system), and it made no difference.

Thanks anyway.

asraskin said

FF 63 Change: "Content blocking added to block third-party tracking cookies or block all trackers."

Check and try different Tracking and Cookie Settings, perhaps?

~Pj

Yeah, I noticed that in the change log and tried both restoring the defaults and opening my browser to all cookies, but neither made a difference.

Make sure you are not blocking content.

Start Firefox in Safe Mode {web link} by holding down the <Shift> (Mac=Options) key, and then starting Firefox.

A small dialog should appear. Click Start In Safe Mode (not Refresh). Is the problem still there?

One issue that seems more common lately is Firefox's Tracking Protection feature. When it is blocking content in a page, a shield icon will appear at the left end of the address bar next to the padlock icon. This article has more info on managing this feature: Tracking Protection {web link}

The problem still occurs in Safe Mode.

And disabling Tracking Protection and cookie blocking similarly had no effect.

This problem is getting worrisome...

Start your Computer in safe mode with network support. Then start Firefox. Try Secure websites. Is the problem still there?

http://encyclopedia2.thefreedictionary.com/Linux+Safe+Mode Starting Any Computer In Safe Mode; Free Online Encyclopedia

This is likely not about cookies, but about renegotiating connection details.

You can check your browser.

• https://www.ssllabs.com/ssltest/viewMyClient.html

As expected, starting in Windows Safe Mode didn't help.

Here are the results of the SSL Client Test:

TLS 1.3 and 1.2 (green): Yes TLS 1.1 (black): Yes TLS 1.0 (orange): Yes SSL 3 and 2 (black): No

TLS_AES_128_GCM_SHA256 (0x1301) Forward Secrecy 128 TLS_CHACHA20_POLY1305_SHA256 (0x1303) Forward Secrecy 256 TLS_AES_256_GCM_SHA384 (0x1302) Forward Secrecy 256 TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 (0xc02b) Forward Secrecy 128 TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256 (0xcca9) Forward Secrecy 256 TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256 (0xcca8) Forward Secrecy 256 TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 (0xc02c) Forward Secrecy 256 TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (0xc030) Forward Secrecy 256 TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA (0xc00a) Forward Secrecy 256 TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA (0xc009) Forward Secrecy 128 TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA (0xc013) Forward Secrecy 128 TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA (0xc014) Forward Secrecy 256 TLS_RSA_WITH_AES_128_CBC_SHA (0x2f) WEAK 128 TLS_RSA_WITH_AES_256_CBC_SHA (0x35) WEAK 256

Server Name Indication (SNI) Yes Secure Renegotiation Yes TLS compression No (green) Session tickets Yes OCSP stapling Yes Signature algorithms SHA256/ECDSA, SHA384/ECDSA, SHA512/ECDSA, RSA_PSS_SHA256, RSA_PSS_SHA384, RSA_PSS_SHA512, SHA256/RSA, SHA384/RSA, SHA512/RSA, SHA1/ECDSA, SHA1/RSA Named Groups x25519, secp256r1, secp384r1, secp521r1, ffdhe2048, ffdhe3072 Next Protocol Negotiation No Application Layer Protocol Negotiation Yes h2 http/1.1 SSL 2 handshake compatibility No (green)

OK, I compared the results for FF 63 and for the Avast Secure Browser, and found one cipher suite that Avast allows but FF does not:

TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (0xc02f)

So I went into about:config and reset security.ssl3.ecdhe_rsa_aes_128_gcm_sha256 to true; now, the problematic websites are displaying properly.

I don't know why it had been set to false, or why everything worked in FF 62 but not in 63, or why the problematic sites required that particular cipher suite.

Thanks to cor-el for providing that link to Qualys SSL Labs' SSL Client Test, and thanks to FredMcD and Pj for their suggestions.

That was very good work. Well done. Please flag your last post as Solved Problem so others will know.

asraskin said

• OK, I compared the results for FF 63 and for the Avast Secure Browser, and found one cipher suite that Avast allows but FF does not:

• TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (0xc02f)

• So I went into about:config and reset security.ssl3.ecdhe_rsa_aes_128_gcm_sha256 to true; now, the problematic websites are displaying properly.

• I don't know why it had been set to false, or why everything worked in FF 62 but not in 63, or why the problematic sites required that particular cipher suite.

Dude! Way to go! Slap me a Digital High-Five!

I don't think I'd thunk of that, now that I think about the thunk for thinking. Something like that. (Grin)

~Pj