Backdoored developer tool that stole credentials escaped notice for 3 months

Supply chain attacks have great reach and often go undiscovered. Hence the popularity of it.

From the article:

The appeal of supply chain attacks to hackers is their breadth and effectiveness. By compromising a single player high in the software supply, hackers can potentially infect any person or organization who uses the compromised product. Another feature that hackers find beneficial: there’s often little or nothing targets can do to detect malicious software distributed this way because digital signatures will indicate that it's legitimate.

In the case of the backdoored bash update version, however, it would have been easy for Codecov or any of its customers to detect the malice by doing nothing more than checking the shasum. The ability for the malicious version to escape notice for three months indicates that no one bothered to perform this simple check.