UPDATE: Wow – the AddThis team have been in touch via multiple channels to confirm they are working on a fix. You know the best thing? From what I’ve seen they’ve thanked everyone that has raised this with them!
I use Plesk for Windows to manage my web hosting servers. It has an excellent ‘WordPress Toolkit’ built in for managing common plugin updates.
Unfortunately, as of today an update to the ‘Share Buttons by AddThis‘ plugin has caused errors on a whole bunch of our websites, all in one go – making it pretty clear the problem is with the plugin.
Interestingly, this has happened before with the exact same error being generated.
For some reason this appears to be affecting people using WordPress management tools such as the Plesk WordPress Toolkit or WP-CLI – either that or those using such tools roll updates out quicker so got hit with it first. A new thread has been raised about the problem here:
Short term, the only way I have found to resolve this is to simply uninstall the plugin by removing the AddThis folder from the plugins folder.
Hopefully the authors will release a fix soon!