Massive Data Breach Hits WK Kellogg Co Amid Global Cleo Software Exploit

Introduction

A major cybersecurity incident has rocked WK Kellogg Co, the American food giant known for household cereal brands like Frosted Flakes and Froot Loops. The company has revealed it was affected by a large-scale cyberattack involving Cleo, a managed file transfer software exploited by the infamous Clop ransomware group. This breach has exposed sensitive employee data and underscores a growing trend of zero-day vulnerabilities being weaponized against enterprise file transfer solutions. Here’s a comprehensive look at what happened, why it matters, and what it signals for the cybersecurity landscape moving forward.

the Incident

What Happened: WK Kellogg Co discovered a breach on February 27, 2025, affecting Cleo servers used to transfer HR-related employee files.
Attack Origin: The breach stemmed from Clop ransomware’s mass exploitation of two Cleo software vulnerabilities — CVE-2024-50623 and CVE-2024-55956.
Date of Breach: Unauthorized access reportedly occurred on December 7, 2024.
Data Exposed: Employee names and Social Security numbers were compromised.
Victim Notification: Affected individuals were offered free one-year identity monitoring and fraud protection through Kroll.
Preventive Measures: WK Kellogg has since worked with Cleo to improve security protocols and prevent future breaches.
Context: WK Kellogg, formerly part of Kellogg’s, became an independent company in October 2023 and brings in an annual revenue of $2.7 billion.
Ransomware Link: Although WK Kellogg did not confirm Clop’s involvement directly, their name later appeared on Clop’s extortion site, confirming their victimhood.
Similar Breaches: WK Kellogg joins a growing list of Clop’s victims, including Western Alliance Bank, which disclosed its breach just weeks prior.
Larger Trend: These attacks are part of a wave exploiting file transfer systems, raising concerns about secure data movement in enterprise environments.
Consumer Advice: Those affected are encouraged to place fraud alerts or credit freezes and monitor their personal information for misuse.

What Undercode Say:

The WK Kellogg breach is a textbook example of the risks that zero-day vulnerabilities in third-party software pose to even the most reputable enterprises. This wasn’t just a case of poor internal security — it reveals a dependency risk that many companies still underestimate.

Let’s break it down:

Software Supply Chain Weakness: Cleo is widely trusted for secure data transfers, especially in HR and financial operations. But attackers targeted it specifically because of its deep integration into sensitive processes.
Zero-Day Exploits at the Core: The attackers used not one but two previously unknown (zero-day) vulnerabilities. This shows a high level of sophistication and planning, likely with a network of reconnaissance operations beforehand.
Clop’s Ransomware-as-a-Service (RaaS) Model: The fact that Clop leaked WK Kellogg’s name on their extortion site reveals the typical playbook — exploit, steal, extort, and publicize to maximize damage.
Regulatory Risk: Exposing Social Security numbers moves the incident beyond PR damage and into legal territory. Regulatory agencies are likely to take a closer look, especially under data protection laws like CCPA or GDPR-equivalents.
Reputation and Trust: WK Kellogg’s consumer base isn’t directly affected — yet. But employee trust is on the line. For a company that just spun off in 2023, maintaining brand integrity is crucial.
Recurring Pattern: This isn’t an isolated attack. Western Alliance Bank and others were similarly affected. This points to systemic risk in using Cleo without robust third-party vetting and monitoring.
Identity Protection – A Band-Aid, Not a Cure: Offering identity theft protection is standard practice, but it does little to address long-term damage. Once SSNs are out, they’re out — and reusable forever by attackers.
The Real Cost: Between regulatory penalties, incident response, monitoring services, and loss of trust, the financial hit will far exceed the costs of proactive cybersecurity investments they could have made.
Future of File Transfers: This event will likely accelerate the decline of traditional managed file transfer (MFT) tools in favor of more dynamic, secure-by-design platforms, possibly involving decentralized encryption or blockchain-led file verification systems.
Call to Action: Enterprises need to aggressively audit third-party software, implement continuous vulnerability scanning, and ensure zero-trust architecture models. Otherwise, today’s HR breach could be tomorrow’s customer leak or full ransomware lockdown.

Fact Checker Results:

CVE Verification: Both CVE-2024-50623 and CVE-2024-55956 are officially recognized as Cleo software vulnerabilities.
Clop Attribution: WK Kellogg was indeed listed on Clop’s extortion site post-breach, confirming their involvement.
Disclosure Timing: WK Kellogg’s February 2025 notification aligns with Clop’s known December 2024 attack wave.

you want a visual timeline of the events or a chart comparing other Clop victims — I can put that together too.