Since you are asking, try this definition of strap hanger from the Urban Dictionary: "A paratrooper that is not listed on an approved jump manifest, and is trying to get a jump on stand-by."
In other words, investors are leaping out by one means or another. Who can blame them, given the financial position of CVS.
As for waiting for the spike, I suggest they are trying to get out of the clutches of the Iron Maiden.