contact form 7 hacked, need help

Over the past 4 day I have received dozens of email like the one below.

It seems my contact form 7 has been hacked. Does anyone know how to fix this?

Thank you
————email————

From: prices slashed hermes birkin bag 35 bi color yellow tabac camel clemence leathe up to 80% off discount <gfdhsdfgdfgdf@gmail.com>
Subject: prices slashed hermes birkin bag 35 bi color yellow tabac camel clemence leathe up to 80% off discount

Message Body:
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