SSL_ERROR_RX_UNEXPECTED_APPLICATION_DATA https://support.mozilla.org/en-US/questions/1169369 In short, the problem is broken support for TLS1.3 in the corperate middleware. A workaround is: 1. Go to about:config 2. Find setting 'security.tls.version.max' 3. Change value from '4' to '3'. ++++++++++++++++++++++++++++++++++++++++++++ ssl_error_rx_malformed_alert https://support.mozilla.org/en-US/questions/1024043 I used the malwareBytes' Anti-Malware, and it worked perfectly, it solved my Problem . . ++++++++++++++++++++++++++++++++++++++++++++ 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 [https://support.mozilla.org/en-US/kb/websites-dont-load-troubleshoot-and-fix-errors?redirectlocale=en-US&redirectslug=Error+loading+web+sites Websites don't load - troubleshoot and fix error messages] http://kb.mozillazine.org/Error_loading_websites [https://support.mozilla.org/en-US/kb/what-does-your-connection-is-not-secure-mean What do the security warning codes mean]