Better Auth: Rate limiter keys IPv6 addresses individually and is bypassable via prefix rotation

Am I affected? Users are affected if all of the following are true: - Their app uses better-auth at a version 1.4.17, or at a v1.5 prerelease tagged = 1.5.0-beta.8. - The apps authentication endpoints serve clients reachable over IPv6. Most managed hosts including Cloudflare, Vercel, Fly.io, AWS...