A single cyber breach can expose millions of people, disrupt essential services, and leave victims dealing with the consequences for years.
The most consequential breaches of 2026 have affected schools, travel companies, home security customers, and millions of ordinary account holders. This ranking weighs the number of people affected, the sensitivity of the exposed information, operational disruption, and the risk of fraud or follow-up attacks.
Editor’s note: This article reflects information available as of July 16, 2026. Breach investigations can change as organizations learn more about what attackers accessed.
How we ranked the breaches
TechRepublic considered four factors:
- Number of people or organizations affected
- Sensitivity of the exposed information
- Disruption to customers or operations
- Risk of identity theft, phishing, or additional attacks
No single factor determined the rankings. Figures provided only by attackers are clearly attributed and were not treated as confirmed victim counts.
5. Aura
Why it ranks No. 5: A breach at an identity protection company created a particularly convincing phishing opportunity.
Aura said an attacker used voice phishing to compromise an employee account and access approximately 900,000 marketing records. Most of the records came from a database connected to a company Aura acquired in 2021.
The affected information included names and email addresses. Aura said its core identity protection systems were not compromised and that Social Security numbers, passwords, credit records, and financial information were not exposed.
Reader takeaway: Be wary of unexpected identity theft alerts. Visit the provider’s website or app directly rather than clicking links in emails or text messages.
4. Panera Bread
Why it ranks No. 4: Millions of customer contact records were reportedly released publicly.
Panera Bread confirmed a breach involving customer contact information. An analysis by the breach-notification service Have I Been Pwned identified approximately 5.1 million unique email addresses among roughly 14 million exposed records.
The information reportedly included names, email addresses, phone numbers, and physical addresses. Those details could help criminals craft targeted phishing messages involving loyalty programs, deliveries, refunds, or purported account issues.
Reader takeaway: Treat unexpected restaurant rewards, refund notices, delivery messages, and account alerts with suspicion. Visit Panera’s website or app directly instead of following links in unsolicited messages.
3. ADT
Why it ranks No. 3: The exposed information reportedly included home addresses and partial identity details.
ADT confirmed that an attacker obtained customer information in a cybersecurity incident.
Reporting and independent analysis linked the intrusion to a compromised employee account. Attackers claimed to have stolen millions of records, while Have I Been Pwned identified approximately 5.5 million affected individuals. ADT did not initially present that figure as its official victim count.
The affected records primarily included names, phone numbers, and physical addresses. Some also contained birth dates and the last four digits of Social Security or tax identification numbers. ADT said payment card and bank account information was not accessed.
Available reporting does not indicate that alarm codes, passwords, or security-system credentials were stolen.
Reader takeaway: Verify unexpected calls from security technicians or support representatives directly with ADT. Never share alarm codes or remote-access credentials with an unsolicited caller.
2. Carnival
Why it ranks No. 2: Nearly 6 million people were affected, with some records containing government identification information.
Carnival reported that the incident affected 5,995,277 people after an attacker used social engineering to gain access to a restricted part of the company’s IT environment.
The affected data varied by person but could include names, addresses, phone numbers, birth dates, membership information, and passport or driver’s license numbers.
Government identification details make the breach especially serious because they cannot be changed as easily as passwords or payment cards.
Reader takeaway: Monitor credit reports and be cautious of travel-related messages requesting payment, login credentials, or passport information.
1. Instructure’s Canvas learning platform
Why it ranks No. 1: The incident combined widespread disruption, private communications, and potentially enormous reach.
Instructure said the security incident involved Canvas user information, including names, email addresses, student identification numbers, and messages sent through the learning platform. The company said it found no evidence that passwords, birth dates, financial information, or government identifiers were involved.
The ShinyHunters extortion group claimed it obtained data connected to nearly 9,000 institutions and 275 million users. Instructure did not independently confirm that 275 million unique people had their information stolen, and the full scope has remained difficult to verify.
The incident also interrupted Canvas access during final exams and assignment deadlines. That operational disruption helped place it above breaches with more clearly established but narrower effects.
Reader takeaway: Students and educators should watch for phishing messages that mention their school, instructors, courses, assignments, or student identification numbers.
Must-read security coverage
FBI cyber incident remains one to watch
A cyber incident involving an internal FBI system also warrants attention due to its potential national security implications.
The FBI confirmed suspicious activity involving an unclassified internal system containing law-enforcement-sensitive information. That included returns from surveillance tools and personally identifiable information related to subjects of FBI investigations.
However, the bureau had not publicly confirmed what information, if any, was stolen. That uncertainty keeps the incident out of the formal ranking.
If investigators confirm that sensitive law enforcement information or personal data was taken, it could become one of the year’s most significant breaches. For companies that work with government agencies, the incident is a reminder to review privileged access, vendor connections, and incident response plans.
What these breaches have in common
Several of these incidents reportedly began with compromised employee accounts or social engineering rather than highly technical software exploits.
The pattern shows why conventional multi-factor authentication may not always be enough. Employees can still be manipulated into sharing codes, approving logins, or granting access.
IT teams should consider phishing-resistant authentication, tighter administrative privileges, alerts for unusual data exports, and stronger limits on the amount of information a single account can retrieve.
What to do after a breach
The right response depends on the information exposed. Useful steps may include:
- Changing reused passwords when login credentials are involved
- Enabling stronger multi-factor authentication
- Monitoring financial accounts and credit reports
- Freezing credit when sensitive identity information is exposed
- Treating messages about the breach as potential phishing attempts
Even if you weren’t directly affected by one of these incidents, the lessons still apply. Every company you trust with your personal information, from your bank and healthcare provider to your favorite restaurant or travel company, could become the next target.
Using unique passwords, enabling multi-factor authentication, monitoring your financial accounts, and responding quickly to breach notifications remain some of the most effective ways to reduce the impact when a cyberattack inevitably reaches closer to home.
Also see: Read how scammers are using FaceTime to target iPhone users and what Apple recommends to stay safe.
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