Package managers seem to be an increasingly popular attack vector. It's only luck that none of the attacks have been particularly malicious yet. Considering how many package manager downloads go to a server in a datacenter, a widely distributed malicious package could control a botnet with extremely high throughput, or wreak havoc on any databases it comes into contact with.

It's only a matter of time before something like this happens. A big part of the problem is that application package managers, like pip or npm, are far less sophisticated than those of operating systems, like aptitude or yum. It needs to be easy for developers to open source their code, and to mark dependencies with precise commit hashes, but the download also needs to be secure and verifiable. There are many difficult tradeoffs to consider in terms of usability, centralization, security and trust.