I would imagine others have wondered on this one. I never did apply the previous Apple Security Update before this last one. Now, with the newest update as of yesterday, I am left wondering if I need to apply that previous one before the latest one. Or, does the latest update cover all the ones before it?
If you use Software Update, it will indicate exactly what updates your specific computer needs - it takes into account what has been done, or not done, previously, & selects the appropriate ones to apply.
Just let Software Update do its thing. I didn't find any updates needed. I just updated QT and the latest Security Update, so I guess the last SU is not needed, as Software Update didn't list it. Thanks.