...except it was not the source code. Apparently right there in the application in cleartext. If what the investigator intended didn't matter, then what the vendor intended doesn't matter, either.

He literally opened the application binary in a text editor to look for clues (despite the fact that there are common tools like `strings` for this) and saw the credentials, and since he'd been specifically hired to fix a problem with the database, he used those credentials to connect to the database. `SHOW DATABASES` would be a perfectly normal thing to type at this point, and apparently once he saw that these credentials granted access to everything he immediately stopped and logged out.

If his lawyers had been better this would have never made it to court. Liability should have fallen on the contract customer, but for certain the design of Modern Solution's software and application were nothing short of wildy irresponsible. If they really face no risk for this, it's time for all German companies to start contracting firms in other countries where idiots aren't allowed to leave thousands of customers data exposed to the first schlub who happens to notice them.

I wonder if there was some kind of software license that stated that the developer was giving the user the key but the user wasn't permitted to use it. At least in that case, he would have known the company's intentions.

I don't think we can otherwise know for sure the company's intentions. If I leave the front door to my house open (or if I tape the key to the outside of the door, to further strain the physical key analogy), is it my intention that people just come on in? We have no idea.