This usually happens when the waste toner auger pipe has an issue. Or if the waste bottle is not changed at the first warning. Especially if you see it with all of the drums.
Normal operation... Waste toner moves out of each drum unit through a small port at the front of the drum. At that point it enters the waste toner pipe (located behind the front inner cover). This toner is then carried to the right towards the waste bottle. The toner exits the pipe from a vertical chute (that is part of the pipe assembly), into the bottle through a port (actually 2 ports). There is an exit port at the bottom of the vertical chute, and a small spring loaded trap door that mates with the waste bottle. The bottle has a larger spring loaded trap door as well. Both ports must be open for the toner to move out of the pipe, into the bottle.
The common issue... Many times the trap door on the pipe gets damaged. There is a tiny tab (not easily detected visually) that allows the pipe door to open when the waste bottle is inserted and fully seated. If this tiny tab breaks off, the trap door remains closed, and the toner cannot exit the pipe. The toner will then back up in the pipe all the way back to the drums. The drums will then push toner out of the mylar seal and make the mess you are seeing. When this happens, you may hear grinding from the drum auger gears, and the drum auger "tails" will break off and enter the waste pipe. This makes the issue worse.
There is no repair for the trap door on the pipe. You could remove the pipe and remove the trap door, or just the spring so that the door remains open all the time, but that would likely cause a mess since toner would drop out of the pipe when the waste bottle is removed. And the broken "tails" are likely to cause a clog in the pipe any way. The waste toner pipe assembly should be replaced to prevent a re-occurrence. Replacing the waste toner pipe is not super difficult, but instructions are recommended.
It would be unusual for this issue to be limited to a single station (only one of the drums). If you are seeing this with the cyan station only, then you may have an issue with the drum drive unit in the back. This drive assembly is much more difficult to replace.
It looks like a bad drum. Make sure the waste auger on the new one turns before you put it in. You will see a black plastic 'gear' on the rear end of the drum. This turns an auger. If it binds up the waste ink has nowhere to go. Also make sure where the waste ink exits the drum in the front that the door opens properly. In your photo you can see where it travels out of the drum into the round mylar opening. Also make sure it is seated properly. It should click in and have slight play. If not the frame of the drum assembly by its handle may be slightly bent.
Anyone ever experience this? Looks like something was grinding against the drum. Its a workcentre 7835. I had replaced all 4 drums at the same time about 2 weeks ago, today i got complaints of a sudden loud grinding noise and cyan covering every sheet. Is this a faulty drum or something more internal? I have spare drums but didnt want to waste one if I didnt have to. Our company is kind of out of the way and service takes a day or two to get to us. Any advice is appreciated.