I actually forgot about this site until today when I got an email notification about it....I would post some stuff but the past month or so I've been really busy and have barely even had time for my job so I haven't made anything though I will start making siggies again now that I have some free time.
It's either a rogue process (which I doubt cause there is literally shit all about it on the web); or it's a Windows application. Many Windows application - especially those which do not create any windows - create "invisible" windows for the purpose of dispatching events. Since these "windows" are never visible, they are often created with systematically generated names (like app.bl87yEIQuTvEqlk4yz4YZQ.6).
The end task box uses the window title as the name of the application, and if application get stuck (maybe waiting on I/O or something), things like what you saw happen