IDIOMS

caught with one's hand in the cookie jar

(idiomatic) Observed or apprehended while committing a theft, especially while embezzling money.

Example: 1969, "Insurance Man Accused in Theft of $400,000," Los Angeles Times, 13 Dec., p. A10:
  A Long Beach insurance broker, who admittedly got caught with his "hand in the cookie jar", has been accused of the theft of $400,000 from the Bank of America.
1989, Claudia Deutsch, "Passing Sentence Before A Trial," New York Times, 19 Feb. (retrieved 24 May 2009):
  Any crisis, whether it is a plant explosion or an executive caught with his hand in the cookie jar, takes on a life of its own.
2007, "The competition was fierce, and the judging a fraught affair," The Times (South Africa), 31 Dec. (retrieved 24 May 2009):
  Frankenmanto was, in fact, a certified kleptomaniac who had to carry a doctor’s letter on her to explain the embarrassing little moments when she was caught with her hand in the cookie jar.