Sourced from next's releases.

v9.5.4

This upgrade is completely backwards compatible and recommended for all users on versions below 9.5.4. For future security related communications of our OSS projects, please join this mailing list.

A security team from one of our partners noticed an issue in Next.js that allowed for open redirects to occur.

Specially encoded paths could be used with the trailing slash redirect to allow an open redirect to occur to an external site.

In general, this redirect does not directly harm users although can allow for phishing attacks by redirecting to an attackers domain from a trusted domain.

We recommend upgrading to the latest version of Next.js to improve the overall security of your application.

How to Upgrade

• We have released patch versions for both the stable and canary channels of Next.js.
• To upgrade run npm install next@latest --save

Impact

• Affected: Users of Next.js between 9.5.0 and 9.5.3
• Not affected: Deployments on Vercel (https://vercel.com) are not affected
• Not affected: Deployments using next export

We recommend everyone to upgrade regardless of whether you can reproduce the issue or not.

How to Assess Impact

If you think users could have been affected, you can filter logs of affected sites by %2F with a 308 response.

What is Being Done

As Next.js has grown in popularity, it has received the attention of security teams and auditors. We are thankful to those that reached out for their investigation and discovery of the original bug and subsequent responsible disclosure.

We've landed a patch that ensures encoding is handled properly for these types of redirects so the open redirect can no longer occur.

Regression tests for this attack were added to the security integration test suite.

• We have notified known Next.js users in advance of this publication.
• A public CVE was released.
• If you want to stay on top of our security related news impacting Next.js or other Vercel projects, please join this mailing list.
• We encourage responsible disclosure of future issues. Please email us at security@vercel.com. We are actively monitoring this mailbox.

---

Core Changes

• Make the image post-processor ignore SVG images: #16732
• Only update lookups for dev overlay if mounted: #16776
• Ensure interpolating dynamic href values works correctly: #16774
• Add automatic reloading when editing GS(S)P methods: #16744
• Update to show build indicator while re-fetching GS(S)P data in dev: #16789

... (truncated)

• 6588108 v9.5.4
• 7108567 v9.5.4-canary.25
• 5d79a8c Update workflow step to restore cache (#17656)
• 4c38e3e fix typo (#17653)
• 241f38e v9.5.4-canary.24
• 7dec911 change anonymous functions to named in docs examples (#17510)
• 1659e4d Update migrating from Gatsby docs. (#17636)
• 06a8b1a Add docs on how to migrate from Gatsby. (#17491)
• 04234cc Update to use hasNextSupport for custom-routes in next export check (#17630)
• 742f5d9 test(create-next-app): increase coverage (#17507)
• Additional commits viewable in compare view

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