[Michielvv]

Although I agree more with the original title, as that would be the exact message I need at this time, I would suggest to then at least also include Sierra, and El Capitan in the title as the fact that the document was updated is most relevant for users of those systems. Maybe reflect that something changed as well. Maybe:

About the security content of macOS High Sierra, Sierra and El Capitan [updated]

[sctb]

Sure thing, we've updated the title to include the other releases, but we'll let the article speak for itself on what was updated and when.