There are two past participles of prove: proven and proved. Mostly, they can be used interchangeably, though in British English, proved is more commonly used.
‘The effectiveness of their mind control helmets hasn’t been proven.’
‘The effectiveness of their mind control helmets hasn’t been proved.’
Both are correct.
The exception to this is that proven should always be used before a noun.
‘They had a proven talent for kitchenware adaptation.’
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