EspoCRM: Pre-authentication stored HTML injection in stream notification emails about email received

EspoCRM is an open source customer relationship management application. Prior to 9.3.9, an unauthenticated remote attacker can send an email to a monitored group or IMAP address, including an email-to-Case address, and place arbitrary HTML in its plain-text body. EspoCRM stores that body and renders it without escaping in Email Received stream notification emails sent to users following the related record, allowing HTML injection and, in mail clients that execute it, JavaScript execution. Earlier sanitization for Post and Mention notifications did not cover this notification path. This issue is fixed in version 9.3.9.