A Wall Street sign is viewed in front of the New York Stock Exchange.Eduardo Munoz | AFP | Getty ImagesThis is CNBC's Morning Squawk newsletter. Subscribe here to receive future editions in your inbox.Here are five key things investors need to know to start the trading day:1. Secret SantaThe three major indexes are coming off back-to-back winning weeks, with the S&P 500 on Friday rising closer to records it set earlier this year. Stocks' advances came as investors geared up for the last Federal Reserve poli ...