Yesterday I happened to check the /wp-content/widget-cache directory and I found HUNDREDS of subdirectories for sites I had never heard of and many of which looked very sketchy (porn sites, etc.). I deleted all the directories and let the plugin recreate my local site sub-directory, and this morning I'm already seeing more unfamiliar directories in there:
The ones that start with "sc" are my site. I've obfuscated the directory name for security reasons.
Why, and how, are other directories for other sites being created in the widget-cache directory? This is VERY disconcerting.