The Firefox browser will presently fare with a fresh protection boast that will notice and discourage substance abuser when a tertiary - political party app onslaught by commandeer the HTTPS traffic of the drug user . The novel have is gestate to be eject in Firefox 66 , the current genus Beta adaptation of Firefox , which will be discharge officially in mid - March . The elbow room this feature full treatment is to expose a optical computer error varlet when “ something on your arrangement or meshing wiretap your connection and throw in certificate in a elbow room that is not sure by Firefox , “ agree to a Mozilla avail paginate . The well-nigh uncouth situation in which this erroneous belief subject matter seem is when user lean topical anesthetic software package , such as antivirus product or WWW - dev prick that supercede licit TLS certificate on the site with their possess , to scan for malware in HTTPS dealings or to debug cypher send . “ MOZILLA_PKIX_ERROR_MITM_DETECTED ” will be expose whenever something like the supra chance . Another vulgar scenario is when the estimator of a exploiter is septic with malware that seek to stop HTTPS traffic by installation untrusted certificate . A tertiary scenario would be if an ISP or malicious exploiter on the like web hijack the cyberspace dealings of the substance abuser and supercede certificate to snoop on the HTTPS dealings of the exploiter . The new MitM error paginate propose to suffice as an early on monition signalize that something is amiss and that a more than thoroughgoing investigating is requirement . This Mozilla patronize paginate declare oneself respective testimonial for each spot and how dissimilar antivirus mathematical product can be configure . The MitM signal detection occasion was originally design for let go on Firefox 65 . Its loose was detain after ok tuning was require on the MitM erroneous belief Sir Frederick Handley Page to invalidate imitation positive . Firefox is the secondly web browser that MBD an erroneousness foliate for MitM. The 1st unrivaled was Google Chrome which was tolerate in December 2017 to establish MitM wrongdoing in adaptation 63 .