As the title indicates, it appears that the latest security update (2020-002) breaks graphics acceleration in some older MacBooks and iMacs running High Sierra and Mojave. Symptoms are black or green video in conferencing apps (FaceBook, Google Meet, Zoom), increasing latency in cursor response, and eventual freezing of the display as the GPU grinds to a halt, requiring a forced restart.
This has been extensively reported at Mr Macintosh, where specific models are listed. These include certain 2015 MacBooks, MacBook Airs, and MacBook Pros, and 2015 iMacs.
Apple’s response so far has been to suggest upgrading from earlier versions of macOS that are affected (High Sierra and Mojave) to the latest Catalina (10.15.4), which is impractical for many users for various reasons.
I’m interested in whether anyone reading this has experienced this problem. If so, I strongly advise you to contact Apple and let them know and urge them to release a fix for all affected versions of macOS.