[@casiepa Moderator 10 years, 8 months ago]

I don’t really know that much of it, but look at the URL you have when you see that message. Probably you have an ‘action’ variable that has no or an incorrect ‘_wpnonce’.
AN example of a correct url : https://www.elegantthemes.com/blog/wp-content/uploads/2015/11/WordPress-Nonces-nonces-in-url.png