"The form submitted did not originate from the expected site"

Howdy.

I'm browsing the forum using Firefox 61.0.2 x64 on a Windows 10 PC (build 17134) and occasionally getting the error message in the title when clicking on the Preview button.

Here's an example where it happened while in this thread;



Is this a possible CDN issue? I'm not doing anything fancy. Going straight to the official website, not using any apps, proxies, or VPNs. It's relatively rare - I'd guess that it happens 1 in 10 times.

Interestingly, it doesn't prevent the Submit or Preview buttons from being displayed - nor does it interfere with the preview functionality. If it helps, the above time it happened was when I'd already started working on one draft for that thread - then in another tab written a post, submitted it, and returned to the previous tab. Haven't tested much, though - could be a coincidence.


Edit: Happened again without me writing multiple posts across different tabs for the same thread.


Edit 2: Haven't tested only browsing the forum in a single tab, yet. I'll try to remember to do so later. Bit busy with work stuff at the moment, so sorry in advance if I forget.


Edit 3: It does not always happen when working on multiple posts across multiple tabs. Going to assume there's no correlation between the two for the moment.

I'm on Firefox as well, and seem to get this every time I try to send a PM. It's only the first attempt, though. If I hit Submit again, it goes through. Quite odd.

Thanks for clarifying. :)