SUMMARY

This is an extremely specific issue. Scrolling on Kickoff with the cursor partially outside of it makes the cursor shadow get gradually stronger until you move it. The same happens without needing to scroll if you open an OBS window with the current screen being shown, leave it visible on the screen, and put the mouse between Kickoff and the taskbar.

PS: To reproduce it while scrolling you don't need OBS open. I'm only citing it because I noticed the bug coincidentally also appeared when trying to grab a screen record of the bug to post here, and I assume it is the exact same bug.

The cursor probably gets duplicated over and over every time something scrolls or when a window capturing the screen is visible. Refer to the attached video for more details.

STEPS TO REPRODUCE
1. Open Kickoff
2. Put the cursor on the place where Applications and Places tabs are located, but leave the bottom of the cursor outside of Kickoff's window, over the taskbar.
3. Scroll

OBSERVED RESULT

Cursor shadow gets darker every time you scroll

EXPECTED RESULT

Cursor shadow should have the same intensity in any situation, just like it does in X.

SOFTWARE/OS VERSIONS
Operating System: KDE neon Unstable Edition
KDE Plasma Version: 5.24.80
KDE Frameworks Version: 5.91.0
Qt Version: 5.15.3
Kernel Version: 5.13.0-27-generic (64-bit)
Graphics Platform: Wayland
Processors: 6 × Intel® Core™ i5-9400F CPU @ 2.90GHz
Memory: 7,6 GiB of RAM
Graphics Processor: Radeon RX 570 Series