OnePlus has finished its investigation into credit card theft and concluded that some users have indeed been affected. Card number, expiry date and security code have been compromised.
The company recommends that you check your credit card statements and alert your bank to any irregular charges which will help you initiate a chargeback. You can contact the OnePlus support team if you need further assistance.
OnePlus is looking into providing a year of free credit monitoring for affected users. This will automatically monitor your card for any shady transactions.
An email sent out to OnePlus customers
Of course, the company is working with a cybersecurity firm to beef up its security systems. OnePlus is still writing up the report on just what happened, but in the meantime check your email and this forum thread for more info.