If you use npm private packages then there's a very serious data leak that you should be aware of. Metadata for private packages was accidentally made available from the public replication endpoint.
I've included the full announcement below:
We need to notify you of a serious security incident that was discovered today, July 2nd.
Starting on June 26th, scoped package metadata was available via the public replication endpoint from npm. This means that third parties were aware of metadata about scoped packages, including private packages. This metadata was limited to:
versions and version publication dates
It's important to make clear that this does not include the packages themselves: package contents and source code were never available. User information such as passwords and billing information was not part of the information that leaked.
If your package metadata contained sensitive information, please take mitigation steps immediately. Because this information replicated, we will be making a public disclosure of the leak. However, to give you time to react (we are aware that it is a holiday weekend in the US) we will be holding off on the public announcement until Monday, July 6th.
We apologize wholeheartedly for this mistake and have taken steps to prevent this error. We are conducting a thorough review of our processes to avoid both this specific problem and any similar errors in the future.
Thank you for your continued support of npm. If you have any further questions or concerns please reach out to firstname.lastname@example.org.
Check your readme files and package names to ensure nothing sensitive has been leaked. This is unfortunate, but npm is handling it promptly and professionally. With any service you rely on for commercial work, like GitHub, Bitbucket, npm, and CDNs, you should review what you publish before it's stored on remote systems.