Hi I have just resolved an issue where the vulnerability was not picked up by Defender.
Please see this link here https://blog.sucuri.net/2016/01/jquery-pastebin-replacement.html
I replaced all the files in wp-includes/js/jquery with an older backup and this resolved the issue but for some reason the changed files did not show that they had been modified at all. I don't know why but they definitely had been because as soon as I overwrote them with the original files the site went back to normal. I have resolved this but want to know if you can build anything into defender to pick up any changes to these files, regardless of whether the system shows it has been modified or not.