fox in the henhouse

English

A metaphor referring to the fox as a predator that would prey on the chickens if given an opportunity to do so.

fox in the henhouse (plural foxes in the henhouse or foxes in henhouses)

(idiomatic, figurative) Someone untrustworthy placed in a position of trust in which they will be harmful, damaging or detrimental for their own personal gain.
- 1995 October 10, David L. Hill, “The Putsch to Enfeeble the Independent U.S. Inventor”, in Impact on U.S. Exporters of the New GATT Patent Accord: Hearing Before the […] House of Representatives […], published 1997, pages 76–7:
  While the Commissioner of Patents is normally expected to understand and to promote the patent system as a bulwark for promoting the U.S. economy, the current Commissioner is, in many ways, a fox in the henhouse, undertaking to destroy that which he was commissioned to protect and to strengthen.

someone untrustworthy placed in a position of trust

Chinese:
Mandarin: 虎入羊群 (zh) (hǔrùyángqún), 虎入羊羣 (zh) (hǔrùyángqún, literally “tiger in a flock of lambs”)
Czech: udělat kozla zahradníkem (cs)
Finnish: pukki kaalimaan vartijana, kettu kanatarhassa
German: den Bock zum Gärtner machen (de) (literally “make the goat into a gardener”)
Hungarian: kecskére bízza a káposztát (literally “entrust a goat with the cabbage”)
Italian: volpe nel pollaio f
Japanese: 猫に鰹節 (ねこにかつおぶし, neko ni katsuobushi, literally “cat in skipjack tuna”)
Livonian: neiku lambõd sieggõ suž lastõd (literally “like a wolf allowed among sheep”)
Norwegian:
Bokmål: sette bukken til å passe havresekken (no) (literally “make the goat watch over the oatbag”)
Polish: lis w kurniku m
Spanish: zamuro cuidando carne (es) m (Venezuela)