Hi there You are my last chance to get this solved. I am from Brazil and trying to access a secure site for the Federal institution that regulates our Tax matters. My setup: MAC OSX last version (El CApitan). Firefox 46.0.1 I use Digital Certificate provided by a USB token. It uses safenet authentication client (https://serviceportal.safenet-inc.com ). While accessing the page (you can see the figure 1) I click on the ecac button and then on the middle right of the page where there is a button "certificado digital" (figure2). The site prompts me a window to choose the certificate I want to use (figure 3). I hit OK, the USB token light flashes (which means it has been accessed) and I am logged. See on figure 4 that I am completely authenticated with my data on top of the screen. The problem now starts: When I click in any option of the site I got the non secure warning with no option add an exception. The error code : SEC_ERROR_UNKNOWN_ISSUER (figure5)