XSS detected when trying to ask a question?

Question

Toaster

... I saw this when I tried to ask a question. FF Browser current version. How could the computer check. There are no problems anywhere else.
What is it?

Answer 1

I answer myself. Correspondence with support:

Apparently, it's still in some kind of expansion.
It was Firefox users who wrote to us about such a problem, for some the problem disappeared after a banal update, for someone - after disabling a number of add-ons.

Then my follow-up question: " So no one in Toaster will deal with this problem? "
And the answer is:
More shortly... If the answer was written not proceeding from my this question. That was addressed only by FF users. The toaster does not do this, these are black problems.
Therefore, I suggest that those who come across here, be noted. In theory, by comparing the lists of extensions of several users, you can literally find a couple of potential culprits without having to "catcher the ostrich in the desert"

Answer 2

The same thing happened to me in a fox under Linux. What is the problem and did not understand. Maybe in plugins. Because the fox and Linux of the same version worked fine on the laptop.

Answer 3

I have such an error if I about:configset network.http.sendRefererHeadera value other than the default value ( 2) in the settings.