I would like to suggest an important update to the mjml dependency used in the nest-modules/mailer project. Currently, the project uses version "4.15.3" of mjml, which depends on html-minifier. However, html-minifier in this specific version has been identified to contain a critical vulnerability known as ReDOS (Regular Expression Denial of Service).

The fix for this vulnerability was implemented in version "5.0.0-alpha.4" of mjml, where html-minifier was replaced by htmlnano. htmlnano not only resolves the aforementioned vulnerability but also improves overall performance in HTML minification.

I downloaded the project locally, replaced the mjml version to "5.0.0-alpha.4", and made the necessary changes to ensure compatibility. After the change, I ran all the project tests, which passed without any problems.

I strongly recommend updating the mjml version in the project to ensure the security and performance of the email module.