Thunderbird does not run scripts in emails. It does however try and load remote images if you have that feature turned "on" and Ebay along many other "marketers" like facebook, linkedin and twitter use images in emails that execute scripts on their servers when the images are loaded. While this is not a security risk, as only an image comes of it, it does allow them to track your usage of their email and the links they contain. Including forwards usually.

Thank you for the explanation. Unfortunately, explaining why by who and how, doesn't deal with the original question - How to stop it?

So the post will be marked Helpful - NO and continue as unsolved until someone can say how to turn off these invasions.

If the scripts are related to remote content, setting View/Message Body As to Simple HTML or Plain Text might help, as both modes ignore remote content.