Job Change while H1b extension still pending

I agree that this is dangerous. You are authorized to work and are in a status authorized by the Attorney General. But this case would be one of the so called "bridge" cases, where your new requested status depends on the grant of the previously requested status. So, CIS waits to see what happens with the previous request. If that is granted, this new request may be granted. But if the previous request is denied, say, because the previous employer withdraws the petition, or if CIS issues a Request for Evidence the employer would no longer bother to respond to, then the pending case is denied, and your new case would be denied a change of status, and you would have to go try to explain to the Consulate how you have not violated your status. It would be a real mess. Far better to wait.