Hello Firefoxers I currently use a Konica Minolta bizhub C308 MFP at my office. We have user authentication setup to keep track of printer usage. My user name and password are saved in the Konica Minolta driver on my iMac (OS 10.12.2) so it doesn't have to be re-entered for every print. After updating to Firefox 50 in December all print jobs from OS X running Firefox 50 fail at the MFP with a "Login Error". Printing from all other applications still work as expected. I have contacted Konica Minolta support and the issue was escalated to the driver developers who researched the problem extensively. They concluded that Firefox is not sending the authentication information needed by the printer to authenticate the print. I found a similar bug report on your site from a couple weeks ago (https://bugzilla.mozilla.org/show_bug.cgi?id=1330379) using a Savin printer, so this appears to be across multiple manufacturers. Below is Konica Minolta's response. We have confirmed that this symptom occurs because of the malfunction of Firefox application,regardless to PS driver. After a deep investigation, we realize that Firefox(Version50.0) does not pass the driver settings to the spooler. Therefore,those neccessary PJL commands are not written in the print data, causing "Login Error" on MFP during user authentication printing. From the capture data retrieved from MFP, we know the following information is not included in the print data sent by the driver. @PJL SET USERNAME = "ops" @PJL SET HOLD = OFF @PJL SET BOXHOLDTYPE = PRIVATE @PJL SET KMUSERNAME = "konica" @PJL SET KMUSERKEY2 = "2F575AB33A772D02D189CFBDE48D16F1" @PJL SET KMCERTSERVTYPE = NONE @PJL SET KMCERTSIMPLEAUTHREQ = OFF @PJL SET CHAPTERMODE = OFF @PJL SET IMAGESHIFT = OFF @PJL SET EDGEMATCHING = FINISH @PJL SET OUTBIN = DEFAULT @PJL SET JIMONMODE = OFF @PJL SET DTSTPMODE = OFF @PJL SET PAGESTAMP = "NONE,1,1" @PJL SET HFSTPMODE = OFF @PJL SET PLANESINUSE = 3 This symptom does not occur if Firefox like Version 48.0,38.0,30.0 are used because these versions of the Firefox pass the driver settings to the spooler. As we conclude this symptom is related to Firefox itself, it is difficult to solve this symptom by modifying the driver. As a workaround, please use other web browser such as Safari if you wish to use user authentication to make a print. Please let me know if there is a fix for this or if it can be corrected in an update. Thank you. Drew