I have startup feedback set to "Passive busy cursor". When an application starts and the cursor appears for a few seconds, if I move the mouse, the icon attached to the cursor leaves traces on the screen.

Reproducible: Always

Steps to Reproduce:
1. Set launch feedback to "Passive busy cursor"
2. Enable the "Startup feedback" KWin effect
3. Start Firefox or Thunderbird (or anything else which takes a few seconds until the icon disappears)
4. Move the cursor
Actual Results:  
The startup feedback icon leaves traces on the screen.

Expected Results:  
There should be no glitches.

Everything looks all right if I disable the effect in KWin, or if I disable compositing.

If I use the "Blinking cursor", I get no traces, but the blinking icon is clipped instead of being displayed in its complete size - the damage area doesn't seem to be all right either.