For a long time, basically since I installed Jenkins for my company to use, all "description" fields have been changing to AD_Login. We use the ec2 plugin so the description for which slave was instantiated for a specific build is always named AD_Login. This wouldn't be a huge deal and I kind of put it on the back burner, but now it's changing password fields for our Windows AMI profiles so it became a huge priority for us as no one can build on a Windows instance.
I did as much digging around as me and one other person could. We googled everything we possibly could and found nothing, not even leads. We grep'd the entire server that master Jenkins is sitting on for any mention of AD_Login and sifted through almost 1 million lines to get nothing.
It happens any time configuration is reloaded from disk, when you first go to /configure it will update every description to be AD_Login, if you change this and use the apply button you can get around it until configuration is reloaded. $JENKINS_HOME/config.xml shows correct values after this save but only until server restart or configuration reload.