This stops you from forgetting that curl or wget | bash is a terrible idea.
Runs a series of regular expressions over your clipboard and checks for curl or wget commands which pipe to a shell such as:
curl https://example.com | bash
wget -O - http://www.example.com | sh
If detected the extension replaces them with
# Clipboard cleared by shellblock #
While this extension wont prevent you from doing something stupid it'll hopefully make you stop and think twice.