Update Now!
To the tune of "Jingle Bells"

Browsing through the Web
On a Win XP PC
Clicking random links
To see what I could see

Nothing looked amiss
No warnings to be seen
But there I was on Christmas Eve
With malware on my screen

Chorus:

Update now, update now
Update all the way!
Oh, what fun you will not have
With malware in your day.

Update now, update now
Update all the way!
Oh, what fun you will not have
With malware in your day.

A day or two ago
A pop-up did appear
"Update now," it said
I canceled with no fear.

My antivirus, too
Expired late last year
I thought I'd save a buck or two
But now I'm paying dear.

(chorus)

Can't get enough holiday infosec songs/poems? Here are a couple more: "A Nightmare Before Christmas" and "Grandma Got Infected by a Trojan."