D flip-flops, but no feedback loops: impossible?
The D type flip flop needs feedback from its inverted Q output to divide frequency by two. That's the short and long story: -



The way a D flip flop works is simple. Positive clock edges latch the state of the D input at the time the edge rises. Therefore by the time the QBAR output has changed state (some few nano seconds later), its previous state has already been latched so there are no glitches.