security update 2015-001 installed 4 times in 30 days

Hi, software update has prompted me to install security update 2015-001 four times in the last 30 days, as per the list that software update shows, with my latest update happening today. I restarted my computer, and then the update prompt happened, and I installed/restarted again. I don't see any indication of updated versions, they all are listed as 1.0 .

I've stayed away from Yosemite up to now as well, running 10.9.5 on an older imac.

Is this normal?

Is it possible that security updates can be removed by malware infested websites?

Or any other explanations?

Thanks so much any help or insight...

Mark