Vercel says some of its customers’ data was stolen prior to its recent hack

App and website hosting giant Vercel on Thursdays said hackers had accessed some of its customers’ data before the company discovered its recent data breach, suggesting that this incident may have broader security implications than initially known.

In an update on its security incident page, Vercel said it had identified evidence of malicious activity on its network preceding the early-April breach after it expanded its initial investigation.

“We have uncovered a small number of customer accounts with evidence of prior compromise that is independent of and predates this incident, potentially as a result of social engineering, malware, or other methods,” the update reads.

Vercel also said it discovered more customer accounts compromised by the April incident, but did not disclose details, only saying that it had notified customers known to be affected so far.

The San Francisco-based app and website hosting company initially said its internal systems were breached after an employee downloaded an app made by software startup Context AI, which hackers abused to gain access to the employee’s work account, and subsequently, Vercel’s systems.

The new update suggests the data breach may be larger in scope and could have lasted longer than initially thought.

In a post on X, Vercel CEO Guillermo Rauch confirmed that the hackers who compromised Vercel have been active “beyond that startup’s compromise,” referring to Context AI, which confirmed an earlier breach of its systems in a post this week.

A Vercel spokesperson declined to comment beyond the update on the incident page. They would neither confirm how many customers the breach now affects, nor say how far the second compromise dates back.

Vercel has not yet confirmed how the hackers broke into its systems, but Rauch pointed to early signs that the hackers relied on malware that compromises computers “in search of valuable tokens like keys to Vercel accounts and other providers.”

Rauch may be referring to information stealing malware, or infostealers, which often masquerade as legitimate software. When installed, the malware collects and uploads sensitive secrets from the victim’s computer, including passwords and other private keys, allowing hackers to enter any system that those keys allow access to.

“Once the attacker gets ahold of those keys, our logs show a repeated pattern: rapid and comprehensive API usage, with a focus on enumeration of non-sensitive environment variables,” said Rauch.

The hackers used the hijacked Vercel employee’s account to gain access to some of the company’s internal systems, including customer credentials that were not encrypted.

Rauch’s comments appear to add weight to earlier reporting by security researchers that a Context AI employee’s computer was infected with infostealer malware after they allegedly looked up Roblox game cheats.

It’s not yet known how many customers are affected by the Vercel breaches and customer data thefts. Both Vercel and Context AI have suggested that the breach may affect more companies, and that more victims may come to light.