Third-party game key seller Kinguin is issuing refunds to those who found their games deactivated through Ubisoft's Uplay service.
Customers which purchased keys for Assassin’s Creed: Unity, Far Cry 4, The Crew and Watch Dogs are affected.
Kinguin said 4,600 customer tickets were submitted over the last 72 hours and 35 out of 3,400 of its merchants were affected. The firm estimates that €148,377 or around £110,720 will be refunded to customers.
All merchants, in cooperation with Kinguin, "have been and will continue" to issue refunds, the seller posted on its website.
Kinguin was told the deactivated game keys were acquired and then sold by an "unidentified individual from Russia."
"Official information released by Ubisoft and Origin claim that fraudulent credit cards were used to acquire Ubisoft keys through Origin platform," wrote the firm's marketing boss Bartlomiej Skarbinski in a blog post.
"Neither we nor other companies in the market have possibility to verify these claims. Merchants have [stated] that an unidentified individual from Russia acquired these keys. How exactly - we do not know. Those keys have been offered to many merchants in the market.
"From what we know now price offered for these keys was so low that most merchants refused to buy the goods. 35, mostly minor, merchants from Kinguin accepted the offer. These merchants now claim that their “source” disappeared and that they were left hanging."
Skarbinski said this is the first case where thousands of customers are being affected, and when all affected are accounted for, "the number could be reaching tens of thousands."
"It seems odd to us that with such big quantities involved 'somebody' bought these via credit card or cards from Origin without any suspicion raised during the purchase process," Skarbinski continued.
"We at Kinguin do not claim ourselves technologically more advanced than Ubisoft or Origin, however, we do verify big or unusual purchases. We believe these platforms must have access to anti-fraud e-commerce tools that should raise alarm flags in such cases."
Skarbinski said in the future, merchants need to pay more attention to to "who business partners are" and avoid risky transactions.
Earlier today, another third-party eBay-esque key seller, G2A, said customers with deactivated game keys will receive compensation via a new code for the game or the money back - if there is verification Ubisoft deactivated the game key.
Ubisoft stated earlier deactivated keys were fraudulently purchased through Origin, which caused EA to remove all Ubisoft products to prevent any future fraudulent purchases.
At present, the customers which purchased keys for Assassin's Creed: Unity, Far Cry 4, The Crew and Watch Dogs are affected.