What are zero-day flaws, and should you trust your dating app?

Technology correspondent Tony Grasso looks at Microsoft's rollout of a security patch for some critical flaws, including one being actively used in conjunction with Chrome. Apple is also moving to patch three zero-day flaws - so what are they? Dating app OKCupid has a flaw where people can read your messages, so how much should you be trusting an app with your most personal chats?