A vulnerability in better-auth versions prior to 1.6.11 allows an attacker to perform account takeover via OAuth auto-linking to an unverified pre-registered email. The flaw arises because the OAuth callback implicitly links accounts based only on the OAuth provider's email verification claim, ignoring the local user's email verification status. This enables an attacker to pre-register a victim's email with an unverified password login and later have the victim's OAuth login linked to the attacker's account, granting persistent access. The issue bypasses the requireEmailVerification setting and affects all OAuth and SSO sign-in flows calling handleOAuthUserInfo. The vulnerability is fixed in better-auth 1.6.11 by requiring the local email to be verified before implicit linking.