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Incident Report: User Account Takeover

What happened?

A PyPI user's account was taken over and used to remove the user's ownership of 4 projects. This was not a malfunction of PyPI or using any vulnerability, rather the user's account was not sufficiently protected against account takeover.

The attacker added themselves as a collaborator to these projects, and removed the original owner. None of the projects had any modifications made to them other than ownership changes.

After the attacker completed ownership changes, they deleted the user's account.

PyPI Admins were informed by the user via email, blocked the attacker's access to the account, and restored the user's ownership of their projects.

No further compromise was made, and existing packages were not modified.

Read on for more details.


all times are in UTC

System timings are from project ownership changes and email notifications. When a user's account is deleted, the account's data is removed immediately, thus we do not have timing of when the attacker gained access to meisnate12's account.

Date: 2023-11-22

  • 08:42:33 new user account dvolk created

(this is the first of 4 packages, only describing one here)

  • 08:44:55 meisnate12 account invites dvolk to be a collaborator on arrapi
  • 08:47:25 dvolk accepts the invitation
  • 08:47:35 dvolk removes meisnate12 as a collaborator on arrapi

(repeated for tmdbapis, nagerapi, pmmutils)

  • 08:50:27 meisnate12 account is deleted

No further actions by dvolk were observed after this point.

  • 14:33, receives an email from the address associated with meinstate12's account:

    I was removed as the owner of arrapi, tmdbapis, nagerapi, and pmmutils. Then my account was deleted so I have no way to log in anymore. My username is meisnate12. What are my next steps here.

  • 14:46 A PyPI Admin responds with:

    Thanks for the report. We've frozen the account in question while we look into this.

  • 14:44 PyPI Admins discuss options in PyPI Admins Slack channel with two other PyPI Admins

  • 14:46 A PyPI Admin disables the dvolk account

After investigation, PyPI Admins determine that the account was compromised, but the attacker did not change any of the projects' data.

We decide the correct course of action is to manually restore the deleted user account, and restore the user's ownership of their projects.

  • 15:53 PyPI Admins close the incident

What can we learn from this incident and improve?

An ounce of prevention is worth a pound of cure

We integrate with HaveIBeenPwned to check a user's password against their service on every login. Unfortunately, the password in question had not previously surfaced in a breach that HaveIBeenPwned knows about, so this didn't prevent the attack.

One of the best tools we have to date to prevent account takeover is Two-Factor Authentication (2FA, or MFA - multifactor auth).

If this user account had 2FA enabled, the attacker would not have been able to take over the account without access to the user's second factor (TOTP app, WebAuthN device, or passkeys).

We have already taken steps to ratchet down usage of PyPI without 2FA enabled.

This encouragement will turn into enforcement at the end of 2023.

We still have a use case where an infrequent user of PyPI, with an account created long before 2FA was available, is still able to log into their account without 2FA, in order to enroll a 2FA device. Read more about this issue and some ideas for resolution.

Deleting things can have unintended consequences

When a user account is deleted, all the account's data is removed. We have a mechanism in place today that prevents a user account from being deleted if they are the sole owner of any projects, to prevent orphaning projects.

In this case, the attacker was able to remove the user's ownership of their projects, and then delete the account.

We have previously entertained ideas on how to prevent full deletions without PyPI Admin intervention, but have yet to settle on a solution. See this tracking issue and for more details. It's not as simple as it sounds.

Even if we continue to delete resources immediately, we should entertain what we can do to preserve some of the details we might need to investigate further. This issue tracks that effort.

If you see something, say something

When collaborators are added or removed to a project, or an account is deleted, we email the address on file.

We were informed of the incident by the impacted user, who still had access to the email account associated with their PyPI username.

Here are a few things you can do to help protect your PyPI account:

This user's diligence in reporting the incident to us helped prevent further compromise.