See the documentation here: https://docs.mendix.com/releasenotes/security-advisories/
And you can subscribe to the Siemens CERT services here: https://new.siemens.com/global/en/products/services/cert.html
On that first page there are also the URL's for the RSS feed: https://cert-portal.siemens.com/productcert/rss/advisories_mendix_products.rss
And there is also a special section in the Mendix slack.
Right, the links have the information that we need, thanks a lot for your help.