I would normally not quote the Daily Mirror, but these are exceptional circumstances: “Banksy wall art vandalised with giant penis in overnight spray paint attack”. The work in question is “Art Buff”, a picture of a elderly woman looking at an empty plinth. This is what the mural looked like before:
And this is what it looks like now:
— Kyle (@wickedheadrush) October 13, 2014
This is as conceptually convoluted as a Borges novel; some kind of contemporary art world version of a dream within a dream: before the mural was vandalised, the building owner had added a sheet of protective plastic sheeting to protect the work (how they knew it was Banksy in the first place remains unclear).