GHSA-MFXH-VP55-7GC6 Contao: The registration module re-sends activation mails

ModuleRegistration::compile reaches its follow-up registration branch on any POST to a page carrying the module. That branch checks neither FORMSUBMIT nor the captcha result computed immediately above it, and resendActivationMail leads to OptInToken::send, which has no rate limit at all. Impact...