Cybercriminals have found a new way to exploit weak email authentication in Zendesk, using it to launch large-scale “email-bomb” attacks. These attacks flood victims’ inboxes with hundreds or even thousands of messages, many of which appear to come from trusted companies. By abusing Zendesk’s customer support system, attackers make the emails look legitimate and difficult to trace.
The root cause of the issue lies in how some Zendesk configurations handle incoming emails. When proper authentication checks like SPF, DKIM, or DMARC are missing or too lenient, attackers can easily spoof messages. This allows them to route mass emails through multiple Zendesk customer accounts, creating the illusion that many legitimate organizations are contacting the same person.
Zendesk has confirmed that it became aware of these malicious activities and took quick steps to address them. The company’s engineers have implemented stronger authentication methods and improved email validation processes to prevent similar abuse. These changes help block spoofed messages and stop attackers from using Zendesk’s infrastructure to send harmful or misleading content.
The scale of the attacks has raised concerns among cybersecurity experts. Because Zendesk is used by thousands of organizations worldwide, such abuse can spread quickly and impact many victims. The email floods can cause confusion, disrupt operations, and make it harder for real customer support messages to reach their destinations. In some cases, attackers use this chaos to hide more targeted or threatening messages among the clutter.
Security researchers have also pointed out that this issue follows a pattern seen earlier in 2025, where cybercriminals misused customer support platforms for phishing and impersonation campaigns. These findings suggest that attackers are shifting their tactics from direct spam servers to abusing trusted third-party systems, making detection and blocking far more difficult.
Experts recommend that all Zendesk users review their email security settings immediately. Organizations should enable strict SPF, DKIM, and DMARC enforcement, as well as monitor their systems for any sudden surge in ticket creation or email volume. Any unusual activity could be a sign that the platform is being misused to distribute spam or malicious messages.
For individuals who find their inbox flooded with strange or threatening emails, the advice is simple: do not click on any links or reply to the messages. Report suspicious emails to the mentioned company or your email provider, and if the volume is overwhelming, contact your IT or security team for support. Ignoring or deleting the messages until the situation is under control is often the safest option.
Zendesk’s quick response and system improvements are expected to reduce the ongoing attacks. However, cybersecurity experts warn that attackers constantly adapt, and platforms must keep strengthening their authentication and monitoring systems. In today’s environment, even trusted tools can become attack surfaces if not properly secured and trust, once exploited, can quickly become a weapon.
Stay alert, and keep your security measures updated!
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