My company is running IE 11.0.9600.17280 on our desktops. We are currently unable to attach files to tasks. When we try to attach a file from our desktop, IE asks if we want to "save or open files?access_token=" and then a big long string. I grabbed a screenshot: https://dl.dropboxusercontent.com/u/30118158/producteev-error.png If you try to open or save, nothing happens (the save fails); all you can do is cancel and not upload your file.
I can upload the exact same files using Chrome without a problem. No open or save dialog pops up.