Umbraco.Forms has HTML injection vulnerability in 'Send email' workflow

Umbraco Forms is a form builder that integrates with the Umbraco content management system. Starting in the 7.x branch and prior to versions 13.4.2 and 15.1.2, the 'Send email' workflow does not HTML encode the user-provided field values in the sent email message, making any form with this workflow configured vulnerable, as it allows sending the message from a trusted system and address, potentially bypassing spam and email client security systems. This issue affects all (supported) versions Umbraco Forms and is patched in 13.4.2 and 15.1.2. Unpatched or unsupported versions can workaround this issue by using the `Send email with template (Razor)` workflow instead or writing a custom workflow type. To avoid accidentally using the vulnerable workflow again, the `SendEmail` workflow type can be removed using a composer available in the GitHub Security Advisory for this vulnerability.