Mac OS Catalina now adds in ‘protection’ against plugins. This means that unofficial Photoshop plugins trigger an “unidentified developer” warning and won’t work.
“WebPShop.plugin” cannot be opened because the developer cannot be verified.
They are marked by OSX with a quarantine flag. This includes the very useful WEBP plugins from WebmProject and Telegraphics.
Happily there’s a workaround, which it took me quite a while to find, so I’m reproducing it in case that helps other find it more quickly.
Open up terminal. Type this command and then the name of the plugin.
sudo xattr -r -d com.apple.quarantine
sudo xattr -r -d com.apple.quarantine /Applications/Adobe\ Photoshop\ 2020/Plug-ins/WebPShop.plugin
(In case you were not aware, you can right click the plugin file and COPY, then PASTE in terminal and it will paste the full path and filename.)
Both these useful plugins are available free here: