This is related to the forum usage itself. It happens sometimes and is really annoying.
I happen to leave my browser tabs open for weeks, while the computer itselfs goes to sleep/suspend. I usually just refresh pages on existing tab. That's the way I use this forum too.
Today, I refreshed some search result page to see if new questions or answers appeared. There was an unanswered question, which I openned in a new tab. I did see my avatar on the upper-right corner, which seems to confirm I am actually logged-in.
After typing my long answer, I was greated with the https://community.victronenergy.com/static/csrfAttackDetected.html page... Going back to the previous page left the answer text editor empty... There is no way I can retreive the text I typed, and I'm not enclined to type it a second time.
I'm now copying this very text elsewhere before submitting my question, just in case.
Since this is not the first time, and leads to lost answers, I guess this problem should be solved by the forum software...