Rocket.Chat exposes the sendForgotPasswordEmail Meteor method without a DDP rate limit, so an unauthenticated caller may invoke it as often as it likes. The method is reachable over DDP and over the HTTP route POST /api/v1/method.callAnon/sendForgotPasswordEmail, and it triggers a password reset message for any address that matches an account. With no DDPRateLimiter rule registered for it, a caller can drive an unbounded volume of reset mail at a chosen address from the deployment's own mail sender, and can probe addresses at scale: the method answers true for an address with no account and for a successful send, but false when the address belongs to an account that authenticates through an external provider and Accounts_AllowPasswordChangeForOAuthUsers is off, so repeated calls distinguish that class of account. Later versions register a rule permitting ten calls per minute per client address.