CVE-2026-12417: SignUp & SignIn <= 1.0.0 - Unauthenticated Privilege Escalation via Weak Password Reset Validation via 'reset_activation_code' Leading to Account Takeover

The SignUp & SignIn plugin for WordPress is vulnerable to Authentication Bypass via Weak Password Reset Validation leading to Account Takeover in versions up to, and including, 1.0.0. This is due to the pravelchangepassword() AJAX handler — registered via wpajaxnoprivpravelchangepassword and therefore accessible to unauthenticated users — performing no nonce verification, no capability check, and only a loose equality check between an attacker-supplied resetactivationcode POST parameter and the target user's forgotemail user meta value; when a user has never initiated a password reset, getusermeta() returns an empty string that trivially satisfies this check against an omitted or empty attacker-supplied code. This makes it possible for unauthenticated attackers to change the password of any WordPress user, including administrators, by sending a crafted POST request to admin-ajax.php with action=pravelchangepassword, resetuserid set to the target account's user ID, and newpasswordcustom set to an attacker-chosen password. Successful exploitation allows the attacker to authenticate with the newly set password and fully take over the targeted account, achieving administrator-level privilege escalation on the affected site.