It is impossible to get a definitive count, but it seems like a significant number of GRE and TOEFL scores from Iran were canceled last week. The scores are from tests taken between November and February. A total of 413 people have signed a petition regarding the situation, while a Telegram channel serving as a hub for updates now numbers 105 members.
I spoke to an individual with canceled scores (from December) who has already began studies in Canada. Not surprisingly, he is nervous about what happens next.
It seems that in each case, test-takers were notified that the cancellation was due to unauthorized software running during their test administration.
Affected test-takers have reached out to media outlets covering higher education (not me) and to parties in the USA they think will advocate on their behalf (not me). One imagines this story will be reported on in the near future.