Yes, I made a mistake with respect to 1.2.2. Upstream's official patch is here. I am going to attempt a high urgency upload during the next houw with 1.2.2 + this patch. If that fails for any reason, NMU welcome without delay.
https://chromium.googlesource.com/webm/libwebp/+/4f1839957115fa4713ed745ceb898657361a1195 >