Is ozone an electrophile in the ozonolysis reaction?
Electrons are concentrated on the two terminal oxygens in ozone but remember, ozone exhibits resonance. The electrons can be delocalized across each oxygen through p-orbitals. 



So yes, at first if you think about the reaction in purely Coulombic terms then it doesn't make much sense. Why would electrons go to a region that already has a relative surfeit of electrons? 

But what happens is that by attacking the terminal oxygen, the double bond effectively displaces electrons to the central, electron-deficient oxygen atom. 

I'm sure someone can explain this in much greater detail with reference to molecular orbital theory but I'll leave that to someone else.