Kepes immediately alerted Xero support, but he told the Herald that the Kiwi online accounting software company is probably not to blame.
"This is highly likely to be a PayPal screwup. As such, Xero is likely an innocent party and impacted by their partner's issue," Kepes said.
"It is a cautionary tale about our increasingly connected and cloud-integrated world, however."
Kepes will be better-placed than most to grapple with that challenge. Earlier this month, he was appointed a director of state-owned enterprise Kordia, which has recently been on a drive to expand its privacy and security services.
Xero has around 2.8 million users worldwide, including 446,000 in New Zealand.
But a spokeswoman for the company said early indications were that it was not a system-wide glitch.
"We are conducting a detailed investigation and at this stage we believe this was an isolated incident. Due to customer confidentiality obligations we are unable to comment further and will be discussing this with Ben shortly," she said.
PayPal has been asked for comment.