Can you imagine Google doing something similar? Heck, they're just about to throw the Android rooting community under a hardware-attestation DRM-filled bus.
It was a forgivable-but-negligent decision to write/approve that code in the first place. It was a sign of a bad process that a reported security vulnerability was not escalated to people security-conscious enough to immediately identify this as a major problem.
I don't agree with the outrage. Anyone who has followed DDG knows they're legit. They just need to do a bit better. They probably will.
Their main feature is privacy. They should be at least as sensitive to privacy vulnerabilities as their most aware users.
DDG should announce that they now pay out privacy-related vulnerabilities like this and send the reporter $5k. It would be good honest PR and well worth the expense.