(Reuters) Groupon Inc , which runs the world’s largest online coupon website, was sued on Tuesday by a shareholder who accused the company of misleading investors about its financial prospects and concealing weak internal controls.

Just four days ago, Groupon unexpectedly revised its results for the fourth quarter, its first as a public company to a bigger net loss and said it had a “material weakness” in its internal controls, having failed to set aside enough money for customer refunds.

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