PyPI Blog: Token Exfiltration Campaign via GitHub Actions Workflows

https://blog.pypi.org/posts/2025-09-16-github-actions-token-exfiltration/

76•miketheman•4mo ago

Comments

miketheman•4mo ago

Incident report of a recent attack campaign targeting GitHub Actions workflows to exfiltrate PyPI tokens, our response, and steps to protect your projects.

zahlman•4mo ago

> Attackers targeted a wide variety of repositories, many of which had PyPI tokens stored as GitHub secrets, modifying their workflows to send those tokens to external servers. While the attackers successfully exfiltrated some tokens, they do not appear to have used them on PyPI.

It's wild to me that people entrust a third-party CI system with API secrets, and then also entrust that same system to run "actions" provided by other third parties.

blibble•4mo ago

it's even worse that that

the CI system itself encourages you to import random third party code into your CI workflow, based on mutable tags

which then receives full privileges

the entire thing is insane

NeutralForest•4mo ago

That's why I stick mostly with Github actions and pin the SHA of the commits instead of the tag version.

blibble•4mo ago

yes, it supports it, but it's not the default, is a pain and fills your build file with a load of noise

so very few use it

it's not made obvious that the tag isn't immutable

although you might be happy with the contents of what you've imported right now, who says it won't be malicious in a year's time

people inadvertently give full control of their build and all their secrets to whoever controls that repository (now, and in the future)

making it easy to do the right thing is an important part of API design and building secure systems, and these CI systems fail miserably there

Harmon758•4mo ago

Immutable releases are in public preview and hopefully will make it easier to do the right thing.

https://github.blog/changelog/2025-08-26-releases-now-suppor...

blibble•4mo ago

I don't see how that solves this problem as long as the attacker can delete and recreate a repository

sigstore's main design goal seems to be to increase the lock-in of of "trusted" providers

(the idea that Microsoft should be trusted for anything requiring any level of security is entirely ludicrous)

frenchtoast8•4mo ago

It’s a good first step, but a significant number of GitHub Actions pull a Docker image from a repository such as Docker Hub. In those cases, the GitHub Action being immutable wouldn’t prevent the downstream Docker image from being mutated.

nodesocket•4mo ago

While Python being more widely used than JS, it's interesting the majority of attacks and breaches come from NPM. The consensus seems to be that Python offering a standard library greatly reduces the attack surface over JS. I tend to agree with this, a decently large Flask python app I am working on has 15 entries in requirements.txt (many of which being Flask plugins).

Hasnep•4mo ago

The large attack surface with npm is partly because of all the transitive dependencies used, which means that even if you only pull in a dozen packages directly, you're also using hundreds of other packages. Running `pip freeze` will list a lot of transitive dependencies as well, but I'm sure it'll be less than an equivalent JS project.

zahlman•4mo ago

The most important packages in the Python world don't have a lot of their own dependencies. Numpy has none, for example. The bulk of Numpy is non-Python code and interfaces/wrappers for that; the standard library isn't AFAIK pulling a whole lot of weight there.

nwellnhof•4mo ago

Numpy depends on BLAS and LAPACK.

milkshakes•4mo ago

while those are obviously huge dependencies, i think the claim was about _python_ dependencies

kinow•4mo ago

I also think the same. While in Java the stdlib lacks a few functions, long ago Apache Commons became the de-facto complement for the Java stdlib, being replaced/complemented by other libs over time, and eventually even becoming obsolete with newer versions of Java. But I always had the impression that having Apache Software Foundation components (with a good release/security process) helped Java to mitigate a lot of attacks.

o11c•4mo ago

Javascript is also hindered by the fact that you have to "pay" for every library you download. This encourages a culture of reinventing the wheel, because "I don't need all that," preventing de-factor stdlib supplements from existing.

magnio•4mo ago

https://www.sonatype.com/blog/pytorch-namespace-dependency-c...

https://socket.dev/blog/pypi-package-disguised-as-instagram-...

https://socket.dev/blog/monkey-patched-pypi-packages-steal-s...

https://socket.dev/blog/malicious-pypi-package-targets-disco...

https://socket.dev/blog/typosquatting-on-pypi-malicious-pack...

darkamaul•4mo ago

Huge kudos to Mike for handling this attack and appropriately contacting the maintainers.

I’m also glad to see yet another case where having Trusted Publishing configured would have prevented the attack. That’s a cheap defense that has proven effective once again!

Liskni_si•4mo ago

If you can change a GitHub Actions workflow to exfiltrate a token, what prevents you from changing the workflow that uses Trusted Publishing to make changes to the package before publishing it? Perhaps by adding an innocent looking use of an external Action?

darkamaul•4mo ago

Nothing.

However, exfiltrating a token is much more easy than modifying the workflow itself. A token is usually simply stored in an env variable.

Liskni_si•4mo ago

In general, yes, it is easier to exfiltrate the token because if you can control some of the code that runs with the token available as an env var, you can do whatever.

In the specific case of the attack described in the blog post, though, the attackers added an extra GitHub Actions workflow that sent the token to an external server. That means they had enough privileges to change GHA workflows, and could just as easily change a workflow that used Trusted Publishing.

(It may be possible to configure branch protections or rules limiting who/when can trigger the Trusted Publishing workflow, but it's about as difficult as limiting the secret tokens to only be available to some maintainers.)

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PyPI Blog: Token Exfiltration Campaign via GitHub Actions Workflows

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