Firmware Autopsy

Pull apart a router firmware image and find the secrets the vendor left inside it.

Scenario

Northwind Freight buys LarkNet routers by the pallet because they are cheap. Before the next batch goes onto the depot network, procurement handed security a copy of the firmware update from the vendor's download page with one question: is there anything nasty baked into it?

No device, no login prompt, no running service. Just the flash image. Crack it open, mount what is inside, and see what the vendor left behind: the credentials in the filesystem and the web handler that trusts anyone.