It might be this extension: Share Button for Pinterest. Some users have said that various extensions by Baris Darin opened a page promoting his other extensions.

Pinterest has it own add-on if you need a Pinterest button. See: https://about.pinterest.com/en/browser-button

That's it. Thank you. It is angering and frustrating that Mozilla would allow extensions on their site that would be able to interrupt a person's work with spam. I don't know if you work for or with Mozilla but if so could you pass this along and if not, could you forward an email address for me to contact them?

Thanks.

KimberCTurner said

I don't know if you work for or with Mozilla but if so could you pass this along and if not, could you forward an email address for me to contact them?

I'm just a volunteer and don't have any special access. This is the official contact info for "policy violations":

If you have a question about an Editor's review of an add-on or want to report a policy violation, please email amo-editors@mozilla.org. Almost all add-on reports fall under this category. Please be sure to include a link to the add-on in question and a detailed description of your question or comment.

From: https://developer.mozilla.org/Add-ons/AMO/Policy/Contact