Morgan Stanley has joined the growing list of Accellion hack victims — more than six months after attackers first breached the vendor’s 20-year-old file-sharing product. 

The investment banking firm — which is no stranger to data breaches — confirmed in a letter this week that attackers stole personal information belonging to its customers by hacking into the Accellion FTA server of its third-party vendor, Guidehouse. In a letter sent to those affected, first reported by Bleeping Computer, Morgan Stanley admitted that threat actors stole an unknown number of documents containing customers’ addresses and Social Security numbers.

The documents were encrypted, but the letter said that the hackers also obtained the decryption key, though Morgan Stanley said the files did not contain passwords that could be used to access customers’ financial accounts.

“The protection of client data is of the utmost importance and is something we take very seriously,” a Morgan Stanley spokesperson told TechCrunch. “We are in close contact with Guidehouse and are taking steps to mitigate potential risks to clients.”

Just days before news of the Morgan Stanley data breach came to light, an Arkansas-based healthcare provider confirmed it had also suffered a data breach as a result of the Accellion attack. Just weeks before that, so did UC Berkely. While data breaches tend to grow past initially reported figures, the fact that organizations are still coming out as Accellion victims more than six months later shows that the business software provider still hasn’t managed to get a handle on it. 

The cyberattack was first uncovered on December 23, and Accellion initially claimed the FTA vulnerability was patched within 72 hours before it was later forced to explain that new vulnerabilities were discovered. Accellion’s next (and final) update came in March, when the company claimed that all known FTA vulnerabilities — which authorities say were exploited by the FIN11 and the Clop ransomware gang — have been remediated.

But incident responders said Accellion’s response to the incident wasn’t as smooth as the company let on, claiming the company was slow to raise the alarm in regards to the potential danger to FTA customers.

The Reserve Bank of New Zealand, for example, raised concerns about the timeliness of alerts it received from Accellion. In a statement, the bank said it was reliant on Accellion to alert it to any vulnerabilities in the system — but never received any warnings in December or January.

“In this instance, their notifications to us did not leave their system and hence did not reach the Reserve Bank in advance of the breach. We received no advance warning,” said RBNZ governor Adrian Orr.

This, according to a discovery made by KPMG International, was due to the fact that the email tool used by Accellion failed to work: “Software updates to address the issue were released by the vendor in December 2020 soon after it discovered the vulnerability. The email tool used by the vendor, however, failed to send the email notifications and consequently the Bank was not notified until 6 January 2021,” the KPMG’s assessment said. 

“We have not sighted evidence that the vendor informed the Bank that the System vulnerability was being actively exploited at other customers. This information, if provided in a timely manner is highly likely to have significantly influenced key decisions that were being made by the Bank at the time.”

In March, back when it was releasing updates about the ongoing breach, Accellion was keen to emphasize that it was planning to retire the 20-year-old FTA product in April and that it had been working for three years to transition clients onto its new platform, Kiteworks. A press release from the company in May says 75% of Accellion customers have already migrated to Kiteworks, a figure that also highlights the fact that 25% are still clinging to its now-retired FTA product. 

This, along with Accellion now taking a more hands-off approach to the incident, means that the list of victims could keep growing. It’s currently unclear how many the attack has claimed so far, though recent tallies put the list at around 300. This list includes Qualys, Bombardier, Shell, Singtel, the University of Colorado, the University of California, Transport for New South Wales, Office of the Washington State Auditor, grocery giant Kroger and law firm Jones Day.

“When a patch is issued for software that has been actively exploited, simply patching the software and moving on isn’t the best path,” Tim Mackey, principal security strategist at the Synopsys Cybersecurity Research Center, told TechCrunch. “Since the goal of patch management is protecting systems from compromise, patch management strategies should include reviews for indications of previous compromise.”

Accellion declined to comment.