First here is the video of the actual cake attack on the Mona Lisa. A man disguised as an old lady in a wheelchair gets up and throws a cake at the Mona Lisa:
Now, afterwards, the cleanup begins:
The Mona Lisa has been behind glass since a Bolivian man threw a rock at the painting in December 1956, damaging her left elbow. In 2005, it was placed in a reinforced case that also controls temperature and humidity.
In 2009, a Russian woman threw an empty teacup at the painting, which slightly scratched the case.