UPDATE 1-U.S.-based stock funds post $17.8 bln outflows in latest week - Lipper

(Adds flow data, analyst comment) By Sam Forgione NEW YORK, Aug 27 (Reuters) - Investors in U.S.-based funds pulled $17.8 billion out of stock funds in the week ended Aug. 26 after a plunge in stock markets spurred a flight to funds that hold safer assets, data from Thomson Reuters' Lipper service showed on Thursday. The outflows from stock funds marked the biggest weekly withdrawals since mid-December of last year. Funds that specialize in U.S. shares posted $11.7 billion in out