Stade Francais said on Thursday that it had been the victim of a cyberattack that affected part of its information system.
French media reported that attackers had published identity documents belonging to 18 players as proof of the breach and demanded a ransom, threatening to release the remaining documents if payment was not made by August 15.
"Immediate containment, investigation and recovery measures have been implemented to secure the affected systems and ensure business continuity," the French rugby club said in a statement.
The club said its online sales platforms, including ticketing and merchandise websites, had not been affected and continued to operate normally.
Stade Francais declined to comment on any communications from those behind the attack or on information circulated by third parties. It added that it had filed a complaint with the relevant authorities.
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