Losing your job at a failed startup is hard enough, but now there’s a growing concern about a hidden threat: the potential for your personal data to be stolen. This includes sensitive details like private messages, Social Security numbers, and bank account information.
A discovery with alarming implications
Security researcher Dylan Ayrey, co-founder and CEO of Truffle Security, uncovered this vulnerability. Ayrey is recognised for creating TruffleHog, an open-source project that monitors data leaks involving API keys, passwords, and tokens. After notifying Google and the affected companies, his findings were presented at the ShmooCon security conference.
The vulnerability lies in how Google OAuth, used for “Sign in with Google,” handles domain-level access. If cybercriminals purchase failed startups’ expired domains, they could log in to cloud-based software linked to those domains. These apps, ranging from Slack to HR systems, often hold critical employee data.
Ayrey tested his theory by acquiring the domain of a defunct startup. Using it, he gained access to applications such as ChatGPT, Zoom, and an HR platform that contained Social Security numbers. He noted that the biggest threat is the monetisable data stored in HR systems, such as banking information.
Thankfully, Google confirmed that data stored in personal Gmail accounts or Google Docs is not at risk. However, startups are particularly vulnerable because they often rely heavily on Google’s tools and cloud-based services. Ayrey estimates that tens of thousands of former employees and millions of accounts could be affected, given the 116,000 startup domains currently available for sale.
Limited solutions to a significant problem
Google’s OAuth configuration includes a feature called a “sub-identifier,” which uniquely identifies each Google account. This mechanism should, in theory, prevent unauthorised access, even if hackers recreate email addresses.
However, Ayrey found issues with this system. Collaborating with an affected HR provider, he discovered that sub-identifiers occasionally changed, albeit in a tiny percentage of cases (0.04%). This inconsistency could lock out hundreds of users weekly for large platforms, leading some providers to forgo the feature.
Google disputes these findings, claiming that sub-identifiers do not change. However, as the HR provider reported the issue and not directly through Ayrey’s bug report, it remains unresolved.
Google’s response
Initially, Google dismissed Ayrey’s findings, calling the issue a “fraud” risk rather than a bug. Ayrey acknowledged this perspective, noting that Google’s OAuth system worked as designed, but the vulnerability highlighted broader data privacy concerns.
Three months later, Google reconsidered and awarded Ayrey a US$1,337 bounty for his discovery. This wasn’t the first time his findings were reconsidered—he faced a similar situation in 2021 when a talk at Black Hat prompted Google to acknowledge his work and award him third prize in their annual security research competition.
Despite recognising the issue, Google has not released a technical fix. The company has updated its guidance, encouraging cloud providers to use sub-identifiers, but has not announced further plans.
You may be at risk if you’ve worked at a failed startup. Ayrey advises employees to secure their accounts by updating passwords and unlinking old “Sign in with Google” connections from inactive domains. Being proactive can help mitigate these risks as the tech world waits for broader fixes.
