hi thairis, mozilla cannot "solve" the logjam vulnerability since this is a vulnerability in the configuration of web-servers (that their respective owners, admins would have to fix). all a browser can do (and firefox 39 will do) is to disallow users from accessing insecure servers and displaying an error message instead. until then you can use this mozilla-provided addon: https://addons.mozilla.org/firefox/addon/disable-dhe/

You can also toggle the involved prefs to false on the about:config page.

• security.ssl3.dhe_rsa_aes_128_sha
• security.ssl3.dhe_rsa_aes_256_sha

You can open the about:config page via the location/address bar. You can accept the warning and click "I'll be careful" to continue.

• http://kb.mozillazine.org/about:config