Information Disclosure via Flags override link

Vulnerability Description

Flags SDK is an open-source feature flags toolkit for Next.js and SvelteKit. Impacted versions include flags from 3.2.0 and prior and @vercel/flags from 3.1.1 and prior as certain circumstances allows a bad actor with detailed knowledge of the vulnerability to list all flags returned by the flags discovery endpoint (.well-known/vercel/flags). This vulnerability allows for information disclosure, where a bad actor could gain access to a list of all feature flags exposed through the flags discovery endpoint, including the flag names, flag descriptions, available options and their labels (e.g. true, false), and default flag values. This issue has been patched in flags@4.0.0, users of flags and @vercel/flags should also migrate to flags@4.0.0.

References

• https://github.com/vercel/flags/security/advisories/GHSA-892p-pqrr-hxqr
• https://github.com/vercel/flags/blob/main/packages/flags/guides/upgrade-to-v4.md
• https://vercel.com/changelog/information-disclosure-in-flags-sdk-cve-2025-46332