I have a list of files where I need to remove some lines that have been added yesterday by a spambot. The section I want to remove looks like this:

^M
<script>[...] bunch of malware code [...]</script>

That section seems to have been appended to the files, so I can be relatively sure it's the last lines of each file that contain this part.

Now I know a bit of Linux, but not enough to do this via a command. How would I go about and do this?