These black cat stickers have been popping up on road signs in on Kent and Sussex for the last few years.
No one has claimed responsibility or given an explanation. There are theories but nothing substantiated.
I don't know if it has spread to other counties in the UK.
#CatsofCoSo
@stueytheround @ceruleanbagel not new BTW
2020/21 it started
https://www.kentonline.co.uk/canterbury/news/the-mystery-of-black-cats-on-kent-road-signs-221700/
Throughout Kent there are hundreds of road signs that have a sticker of a black cat peering round in the corners.