This recently happened, and I was able to fix it with the help of the affected poster.

In a nutshell, you might sometimes observe some posts that have some garbage added to the top of the message, along the lines of :

"if(typeof window.__wsujs==='undefined'){window")"

Looking at the entire script code, the word 'Media Ads' stood out - and it's indicative of a malware infection of the Chrome browser.

I'm posting this, and the solution, here, because the moderator that initially interacted with the thread seems to have been overwhelmed by the technical nature of this issue. However well-intentioned, he ended up messing up affected posts and their quotes further :-(

I ended up contacting the affected user (it was always the same user's posts that had this problem) and helped him figure out that it was his Chrome browser that was infected with malware. He followed up a bit later to confirm that he ran a malware scan and had dozens of malware scripts that wee eliminated - and just like that, the problem was resolved.

Posting this here mostly for the benefit of other moderators, so that you know what is going on when you see this sort of thing, and how to fix it. Feel free to PM me should you have my questions.

This is already going on since a long time

read here:

http://www.thaivisa.com/forum/topic/706227-javascript-code-in-posts/

Right. If you see it, let the posters know. That's the way to stop it.

If this is already historically known (thanks for the link) it's worrisome that some mods aren't aware of it. Maybe better communication about these issues.