I find it rather silly to be worried about security given that Apple's one of the largest browser vendors in the world, directly or indirectly via WebKit.

More accurately: all increasing of capabilities in non-immediately-apparent sources IS cause for concern. But that has to be weighted against the exhibited competence of the vendor. I find it unlikely that we-vet-everything our-brand-name-is-safe-computing-experiences Apple wouldn't have considered security in this move.