A 16-year-old boy from Chelmsford was rushed to hospital with serious facial injuries after he was attacked while lights were switched on in Ongar.
The victim was set upon by a group of boys in Ongar High Street during the event at around 8.20pm last Friday (November 28), which was led by TOWIE star Georgia Kousoulou.
Police said his girlfriend was also assaulted while she tried to step in and defend him.
Investigating officer Dc Nicola Hudson from Loughton CID said: "This happened on the night of the Christmas Lights event so the High Street was very busy.
"I would ask anyone who witnesses the incident to contact me."
Any witnesses to the incident or anyone who has information about the assault is asked to contact Dc Hudson on 101 ext 313401.
People can also give information to Crimestoppers anonymously on 0800 555 111 or via www.crimestoppers-uk.org
