Glad to hear (about just around two cases).
Assuming that scale of security related issues maybe it would be possible to ask you to put short message (such as "do upgrade immediately") in a subcategory "security announcements" in the current forum when (accidentally) it would happen again? It should be just ~2 minutes of your time per (hypothetical) incident. WDYT?
Having that category created in advance people could subscribe to it using native Discourse mechanisms and get email (or any other) notification.