I tested the latest Firefox beta using https://cc.dcsec.uni-hannover.de/ and all ciphers supported by Firefox 25 use MAC SHA1, none of them allow SHA-2. Can this be changed? Have Firefox plans to use SHA-2 in the future?
Beside, when I try to access a site that just support SHA-2 MACs, I got an error.
I tested on Ubuntu 13.10 using ppa:mozillateam/firefox-next to have Firefox using NSS 3.15.1 and result the same, no SHA256 ciphers was available. Chrome (with >= NSS 3.15.1) and Opera work fine.