Rear diff leak 04 foreman rubicon

We just bought a used 2004 foreman rubicon 500 a couple weeks ago. Yesterday I notice diff fluid on the garage floor. I’ve read that it may be the seal or a vent that leaks if too much diff fluid was added. The fluid was fairly clear and clean, looked new. Can you guys tell me where that vent is and how to check? This is our first atv so I don’t know much. Thanks

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