Actress Nicole Crowther sparked controversy online earlier this week when she revealed the identities of the programme's "Prom King and Queen".
Her tweet angered some "Glee" fans, who attacked Crowther for spoiling the upcoming storyline. And show producer Brad Falchuk reacted to the unauthorised leak by hitting back with a scathing online response.
He wrote: "Who are you to spoil something talented people have spent months to create? Hope you're qualified to do something besides work in entertainment."
The backlash prompted Crowther to shut down her Twitter blog shortly after the feud and, in her final post, she admitted she had messed up.
According to MTV News, the extra was subsequently notified that she was no longer welcome on the TV set.