Simon Willison

simonwillison.net • June 8, 2026

Package Managers Need to Cool Down . Today's LiteLLM supply chain attack inspired me to revisit the idea of dependency cooldowns , the practice of only installing updated dependencies once they've been out in the wild for a few days to give the community a chance to spot if they've been subverted in some way.

This recent piece (March 4th) piece by Andrew Nesbitt reviews the current state of dependency cooldown mechanisms across different packaging tools. It's surprisingly well supported! There's been a flurry of activity across major packaging tools, including:

pip currently only supports absolute rather than relative dates but Seth Larson has a workaround for that using a scheduled cron to update the absolute date in the pip.conf config file.

This is a link post by Simon Willison, posted on 24th March 2026 .

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This article is one source in a clustered incident — the cluster page carries the summary, timeline and every other outlet covering it.

RubyGems Implements Dependency Cooldowns to Combat Supply Chain Attacks RubyGems has introduced dependency cooldowns in Bundler to mitigate supply chain attacks that exploit newly published packages. This feature delays the installation of packages until they have been available for a specified number of days, allowing time for malicious versions to be identified and removed. Recent attacks have targeted developer credentials, enabling threat actors to inject malicious code into packages. The cooldown system is designed to protect users by preventing the immediate installation of potentially compromised packages. Developers must manually enable this feature, which is disabled by default. RubyGems joins other package managers like npm and pip, which have already implemented similar measures. The move comes in response to a significant rise in supply chain attacks over the past nine months, with notable incidents affecting multiple ecosystems. The first public proof of concept for a related CVE was released on June 6, 2026, highlighting ongoing vulnerabilities in the ecosystem. 2 sources 68

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Simon Willison

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MITRE ATT&CK (1)

Platforms (1)

Tools (1)