Mastra npm Org Compromised: Multiple Packages Trojanized to Drop a Remote Payload via easy-day-js | Blog | Endor Labs

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Blog<br>Mastra npm Org Compromised: Multiple Packages Trojanized to Drop a Remote Payload via easy-day-js<br>A single hijacked maintainer account pushed multiple trojanized packages across the entire @mastra scope in 27 minutes, each carrying a typosquat dependency that runs a remote payload on install. Combined reach is over 28 million downloads a month.

Written by<br>Peyton Kennedy

Published on<br>June 17, 2026

Updated on<br>June 16, 2026

Topics<br>Malware

Summarize with AI

TL;DR<br>An attacker took over the account of a Mastra maintainer and used it to tamper with the project at scale. Over a 27-minute window, they republished the entire @mastra catalog. They left Mastra's own code alone. In each package they changed a single line, adding a hidden link to a counterfeit component named easy-day-js, a lookalike of a widely used tool called dayjs.

Mastra is an open-source toolkit that software developers use to build AI applications and agents. It comes from the team behind Gatsby and is widely adopted: the project's components are downloaded more than 28 million times a month by teams building on top of it. Like most modern software, Mastra is shipped as a set of small, reusable building blocks that other programs pull in automatically. That reach is what made one stolen account so dangerous.<br>easy-day-js is a typosquat. It impersonates dayjs down to the description and the bundled dayjs.min.js, but adds a postinstall hook that runs a dropper. On install, the dropper disables TLS certificate validation, fetches a second-stage payload from a raw IP address, writes it to the temp directory, runs it as a detached and hidden child process, and deletes itself.<br>Three things stand out about this incident:<br>The whole org went at once. This was not one package. It was a scripted sweep of 116 packages in under half an hour, ordered roughly by download count, which points to a hijacked account with publish rights across the entire scope rather than a single rogue release.<br>The carrier packages are clean; the payload is one level down. Every Mastra package is an unmodified library with a single poisoned dependency line. Scanners that only inspect the named package's own code will not see anything wrong. The malicious behavior lives in easy-day-js, and in most of the packages that dependency is never even imported.<br>A pre-staged decoy dependency. easy-day-js@1.11.21 was published a day earlier with no install hook, a clean decoy. The weaponized 1.11.22 landed at 01:01 UTC, eleven minutes before the Mastra sweep began.<br>Affected packages<br>All versions below are malicious and were published 2026-06-17. Pin to the last provenance-backed release of each and treat these specific versions as compromised.

Package<br>Malicious version<br>Published...