Every single avatar I have uploaded for the past 48 hours, ranging in every performance rating from "Good" to "Medium" to "Poor" is now being marked as "Security Check Failed". I own all of these avatars, and most of them are ones that have previously been uploaded fine regardless of rating, some of them I've even been trying to optimize, like the Estellios (The poor ranking one you see).
After five test uploads, every avatar is seemingly immediately marked with this upon upload, and there's nothing I can do to fix it on my end. It's clear to me that something else is triggering it besides the size changes (which there seems to be no size indication in the checks that I can see here, I'd like that to be an option if it's not already), but I don't know what it could be. There's not enough feedback for me to diagnose it.