The football club said it's still investigating the incident and couldn't say if the breach allowed the intruders to access data associated with fans or store customers.
While the club remained tight-lipped about what hackers managed to access, they said the incident didn't impact its primary media channels, such as its website and mobile apps.
"All critical systems required for matches to take place at Old Trafford remain secure and operational and tomorrow's game against West Bromwich Albion will go ahead," club officials said in a press release issued late Friday night.
United officials said they detected and took swift actions to contain the attack, which minimized its impact. The club says it's now working with security experts to investigate the incident and minimize the IT disruption. Manchester police was also notified of the incident.
But Man-U and Liverpool aren't alone. Other UK football clubs were also targeted by spear-phishing attacks and BEC scammers looking to hijack club payments, according to a report published by the UK National Cyber Security Centre in July this year.
The same report also revealed that one unnamed club also suffered a ransomware attack that impacted its access gate turnstiles. The incident was remediated in time for the next match, allowing fans to enter the stadium.