Next.js is a React framework for building full-stack web applications. From 15.0.0 until 15.5.27 and 16.3.8, self-hosted applications using the Pages Router with statically generated or Incremental Static Regeneration pages can key a response cache entry without sufficiently binding it to the source route. A request can replace one page's cache entry with content from a different route, causing the affected page to serve incorrect content to every visitor until revalidation. Applications deployed on Vercel are not affected. This issue is fixed in versions 15.5.27 and 16.3.8.