Pypi Blog: Token Exfiltration Campaign via Github Actions Workflows

Posted4 months agoActive3 months ago

miketheman

76 points

20 comments

blog.pypi.orgTechstory

calmmixed

Debate

60/100

SecurityGithub ActionsPypiCi/cd

Key topics

Security

Github Actions

Pypi

Ci/cd

A recent attack campaign targeted GitHub Actions workflows to exfiltrate PyPI tokens, prompting a discussion on security best practices and the effectiveness of Trusted Publishing.

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Sep 16, 2025 at 5:09 PM EDT
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3 months ago
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Discussion (20 comments)

Showing 20 comments

zahlman

4 months ago

1 reply

> 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

3 months ago

1 reply

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

3 months ago

1 reply

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

blibble

3 months ago

1 reply

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

3 months ago

2 replies

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...

frenchtoast8

3 months 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.

blibble

3 months 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)

nodesocket

4 months ago

4 replies

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).

zahlman

4 months ago

1 reply

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

3 months ago

1 reply

Numpy depends on BLAS and LAPACK.

milkshakes

3 months ago

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

kinow

3 months ago

1 reply

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

3 months 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.

Hasnep

4 months 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.

magnio

3 months 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...

Liskni_si

3 months ago

1 reply

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

3 months ago

1 reply

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

3 months 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.)

mikethemanAuthor

4 months ago

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

darkamaul

4 months 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!

View full discussion on Hacker News

ID: 45268084Type: storyLast synced: 11/20/2025, 1:35:57 PM

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