On October 20, 2021, Sonatype reported that their automated malware detection systems detected multiple malicious packages on NPM. They were klow, klown, and okhsa which introduced a dependency on klown. The incident was reported to NPM on October 15, and the packages were taken down the same day.
Sonatype discovered that klown was published to NPM a few hours after klow was taken down by the administrators, and that klown pretended to be another legitimate package, ua-parser-js. The malicious packages downloaded an executable cryptominer binary during the pre-install phase, and executed it. Luckily, the packages weren't downloaded a significant number of times.
Interestingly, a few days after this incident, the ua-parser-js package was hijacked, and malicious versions with similar cryptomining functions were released on NPM. This incident is written up in greater detail here.
As these seem to have been new packages that were relatively unused, this can be categorized as Negligence since the packages pretended to be another legitimate package. However, this incident is relevant because of its connection to the ua-parser-js incident.