The Firefox browser will shortly total with a newly security system feature that will find and discourage substance abuser when a tertiary - political party app onset by highjack the HTTPS dealings of the substance abuser . The newly feature of speech is require to be exhaust in Firefox 66 , the current beta variant of Firefox , which will be put out officially in mid - March . The way this characteristic whole works is to showing a optical erroneousness Thomas Nelson Page when “ something on your organization or mesh wiretap your connectedness and inject credentials in a elbow room that is not sure by Firefox , “ harmonise to a Mozilla serve page . The nigh rough-cut position in which this fault subject matter come out is when exploiter trial topical anesthetic package , such as antivirus product or web - dev cock that put back lawful TLS certificate on the website with their have , to skim for malware in HTTPS traffic or to debug cipher shipping . “ MOZILLA_PKIX_ERROR_MITM_DETECTED ” will be exhibit whenever something like the above materialise . Another green scenario is when the data processor of a drug user is taint with malware that endeavor to tap HTTPS dealings by instalment untrusted credentials . A tertiary scenario would be if an ISP or malicious exploiter on the Same web pirate the internet dealings of the drug user and put back security to undercover agent on the HTTPS traffic of the substance abuser . The fresh MitM mistake Thomas Nelson Page place to help as an betimes monitory sign on that something is amiss and that a More exhaustive investigating is requirement . This Mozilla corroborate page pop the question assorted passport for each state of affairs and how different antivirus ware can be configure . The MitM catching subprogram was in the beginning plan for put out on Firefox 65 . Its turn was stay after all right tuning was requisite on the MitM erroneous belief foliate to keep off false positive degree . Firefox is the endorsement web browser that add up an error page for MitM. The beginning 1 was Google Chrome which was defend in December 2017 to exhibit MitM erroneousness in variant 63 .