Beautiful, useful extension! But honestly, who installs (and keeps) extensions like this that require your absolute trust???
"Add CSS Peeper? It can: - Read and change all your data on the websites you visit."
Are there really no other less permissive options for extension developers?
Looking at what it does, that seems like a necessary permission and the whole point of the extension. You can always inspect the source code if you're at all unsure...
Where is the link to their repository. Couldn't find one on their site...
Couldn't they update the extension with malicious code at a later point without you noticing?