CornerStone Staffing Solutions Data Breach

CornerStone Staffing Solutions, Inc., a staffing and recruiting agency based in the San Francisco Bay Area with offices across the country, has notified individuals that a November 2025 cyberattack on its computer systems may have exposed their personal information. Companies that collect and store personal data at scale, including resumes, onboarding paperwork, and payroll records, have a responsibility to protect that information from unauthorized access.

CornerStone Staffing Solutions’s Data Breach Investigation

According to public reporting and a subsequently filed class action, CornerStone Staffing Solutions experienced a data breach around November 2025 in which the Qilin ransomware group claimed to have extracted approximately 300 gigabytes of sensitive information from the company’s systems. Qilin publicly claimed the stolen data included more than 120,000 resumes belonging to job seekers as well as additional internal financial documents, and stated the cache included nearly 24 million individual data points. A class-action lawsuit filed in the U.S. District Court for the Northern District of California in April 2026 alleges the stolen information included names and Social Security numbers.

Staffing and recruiting agencies are attractive targets for ransomware groups because their business model requires them to collect and retain large volumes of personal information, including resumes, background-check materials, and onboarding forms, from job seekers who may never have a direct ongoing relationship with the agency after being placed. Once threat actors like Qilin, which has been one of the most active ransomware operations globally, gain access to this kind of aggregated data, the exposed information can be used for identity theft, tax fraud, and other financial crimes long after the initial intrusion. Security researchers who track Qilin’s public leak site note the group has claimed responsibility for hundreds of attacks in the past year, targeting organizations across many industries in an effort to extract ransom payments.

CornerStone Staffing Solutions has not publicly confirmed the full scope of the incident as of this writing, and it remains under investigation. Affected individuals whose resumes, applications, or employment records were on file with the company should watch for a formal breach notification letter describing what specific data of theirs may have been involved.

When Did This Breach Occur?

The data breach is reported to have occurred around November 2025. CornerStone Staffing Solutions began notifying affected individuals and the California Attorney General’s office of the incident in 2026.

What Information Was Breached?

According to public reporting and the subsequent class-action complaint, the exposed information includes names and Social Security numbers contained in job applicants’ resumes and other internal company records.

What You Can Do

If you applied for a position through or were placed by CornerStone Staffing Solutions, consider taking the following steps:

• Monitor your financial accounts and credit reports closely for unfamiliar activity.
• Consider placing a fraud alert or credit freeze with the major credit bureaus.
• Watch for a formal breach notification letter from CornerStone Staffing Solutions and follow any guidance it provides.
• Be cautious of phishing emails or calls referencing a job application or this incident.
• Request a free copy of your credit report at annualcreditreport.com to check for suspicious activity.

File a Data Breach Lawsuit Against CornerStone Staffing Solutions

If you applied for a job through or were employed by CornerStone Staffing Solutions and believe your personal information may have been compromised in this data breach, you may be entitled to compensation. Companies that collect sensitive personal information from job seekers are expected to maintain reasonable safeguards, and when those safeguards fail, the individuals whose data was exposed often bear the burden of the resulting fraud risk.

Contact us at Class Action U, where we’ll connect you with a lawyer skilled in class action lawsuits. If you’ve been contacted about this breach, received notice, or discovered you were impacted, fill out our quick, easy, and secure form to sign up. There is no cost to reach out to our legal partner and no obligation after speaking with someone from our team.