It frustrates me to say this, but one of the plugins I was using to provide social media links, Simple Share Buttons Adder, had snuck in a tracking script into their software. If you have tracking disabled in your browser, then this shouldn't affect you, but nevertheless, software companies need to be less underhanded and I need to be more on top of things. I have since removed this plugin and replaced it with a plugin whose creators are more scrupulous.
If you use this plugin or see a site using this plugin, let the site owners know you want this plugin removed.