Robin
Many thanks @skidoo for your detailed instructions and links to this interessting theme, this was realy great stuff to read. It was a great help while writing my scripts. Sorry for not answering that long, I had my head always buried under different tasks, so my answer got lost those days. What I understood was: There is a severe kernel bug which allows to foist a different script file content while handling the execution of interpretation. Which renders all efforts to increase script security from within an interpreted script useless in the end. But I also understood there is a known patch to help this, it simply never made its way into our kernels. What a pitty.
Windows is like a submarine. Open a window and serious problems will start.