Latest Facebook 18 user agents:

User Agent Platform Device
Mozilla/5.0 (iPhone; CPU iPhone OS 7_1_2 like Mac OS X) AppleWebKit/537.51.2 (KHTML, like Gecko) Mobile/11D257 [FBAN/FBIOS;FBAV/18.0.0.14.11;FBBV/5262967;FBDV/iPhone3,1;FBMD/iPhone;FBSN/iPhone OS;FBSV/7.1.2;FBSS/2; FBCR/Carrier;FBID/phone;FBLC/en_US; iOS 7 iPhone 4
Mozilla/5.0 (iPad; CPU OS 9_3_6 like Mac OS X) AppleWebKit/601.1.46 (KHTML, like Gecko) Mobile/13G37 [FBAN/FBIOS;FBAV/18.1.0.14.11;FBBV/5295262;FBDV/iPad3,3;FBMD/iPad;FBSN/iPhone OS;FBSV/9.3.6;FBSS/2; FBCR/vodafoneUK;FBID/tablet;FBLC/en_GB;FBOP/1] iOS 9 iPad 3
Mozilla/5.0 (iPad; CPU OS 7_1_1 like Mac OS X) AppleWebKit/537.51.2 (KHTML, like Gecko) Mobile/11D201 [FBAN/FBIOS;FBAV/18.1.0.14.11;FBBV/5295262;FBDV/iPad2,5;FBMD/iPad;FBSN/iPhone OS;FBSV/7.1.1;FBSS/1; FBCR/;FBID/tablet;FBLC/en_US;FBOP/1] iOS 7 iPad Mini