Without a bridle, or a saddle, across a thing I ride a-straddle. And those I ride, by help of me, though almost blind, are made to see. What am I?

It started as a typo, now it is a core game taunt. You belong to me, I have dominated you. In cybersecurity, the system has been compromised.

I am another word for piece of, as in piece of glass. It's hard to guess. That is why the answer is in this riddle. What am I?

Guardian of treasures, small yet mighty, turning the key is the only way to free what's held tight.

I speak without a single word, yet still my message can be heard. By flashing light or unseen flow, I tell you when to stop or go.