In August 2025, Google’s Threat Intelligence Group (GTIG) revealed a significant breach caused by the compromise of a third-party email integration. Attackers abused OAuth tokens connected to the Salesloft Drift app, a widely used integration, to access sensitive data and email accounts across hundreds of organizations. This incident exposed how vulnerabilities in third-party email integrations can lead to widespread data exposure and disrupt critical workflows.
Shortly after, Microsoft reported an increase in attacks exploiting OAuth applications and integrations, including malicious apps impersonating trusted brands and abuse of Microsoft Copilot Studio agents to steal OAuth tokens and gain stealthy mailbox access.
These recent incidents indicate a growing and dangerous trend where email is no longer just a messaging platform but a complex ecosystem of APIs, OAuth permissions, and third-party integrations. When these integrations are compromised or misused, they become powerful attack vectors for hackers.
Email integrations are the various technical connections that link your email environment to external systems, tools, and services. These can include:
Together, these integrations enable automation, improve patient and customer communication, and streamline complex workflows. They are indispensable in modern healthcare and business environments.
However, every integration also increases your attack surface. If not properly secured or monitored, these connections can be abused by cybercriminals to bypass traditional email security controls.
Developers sometimes accidentally expose API keys or SMTP credentials in public repositories, configuration files, or CI/CD pipelines. For example, according to Bleeping Computer, in 2023 alone, more than 12.8 million authentication secrets were leaked across more than 3 million public GitHub repositories, with around 90% of those keys remaining valid for at least five days, providing attackers a valuable window to exploit them.
Because API keys function as bearer tokens, possession grants attackers the same access as the authorized service. This can allow them to send phishing emails from legitimate domains or exfiltrate sensitive email content without triggering traditional security alerts.
OAuth simplifies application access to email accounts but can also be a major attack vector. Attackers register malicious apps or trick users into consenting to apps requesting broad mailbox scopes. Once OAuth tokens are obtained, attackers can:
This often bypasses traditional password-based alerts and multifactor authentication.
As with the Microsoft case, attackers have used malicious OAuth apps to send hundreds of thousands of phishing emails while quietly creating inbox rules to hide their presence and maintain long-term access. These campaigns highlight how easily OAuth consent can be abused to scale attacks and evade conventional security controls.
Organizations often depend on third-party services such as CRMs, marketing platforms, and HR tools integrated with email systems. A breach or compromise of one of these vendors effectively grants attackers the integration privileges those apps possess.
These supply-chain style attacks are increasing. The Salesloft Drift breach discovered by Google’s Threat Intelligence Group (GTIG) is a prime example, where attackers abused trusted third-party OAuth tokens to access sensitive data across hundreds of customers.
Organizations often depend on third-party services such as CRMs, marketing platforms, and HR tools integrated with email systems. A breach or compromise of one of these vendors effectively grants attackers the integration privileges those apps possess.
These supply-chain style attacks are increasing. According to The Guardian, “Almost a third of bosses have reported an increase in cyberattacks on their supply chains over the past six months.”
The Salesloft Drift breach discovered by Google’s Threat Intelligence Group (GTIG) is a good example, where attackers abused trusted third-party OAuth tokens to access sensitive data across hundreds of customers.
Read also: What is a supply chain attack and how can it be prevented?
APIs underpinning email integrations often contain vulnerabilities such as:
The Software Engineering Institute’s 2024 report stresses that API vulnerabilities are widespread and rising, with weak identity and access management models among the leading causes. Since modern email systems rely heavily on APIs (transactional emails, security scanning, and workflow automation), these issues translate directly into email risk.
Attackers are exploiting email and integration blind spots at scale.
Together, these data points show that the conveniences we build into email flows are attractive to opportunistic and sophisticated adversaries alike.
Here’s how Paubox’s inbound email solution helps safeguard your organization:
Paubox’s inbound email filters leverage AI-driven malware and phishing detection tailored specifically for healthcare environments. By scanning inbound emails before they reach your mailboxes or integrations, Paubox stops threats that could abuse OAuth tokens or API permissions.
Paubox uses DMARC, DKIM, and SPF validation combined with sophisticated algorithms to block phishing attempts that often exploit trusted third-party integrations. This prevents attackers from tricking users into approving malicious OAuth app consents or clicking on harmful links.
Unlike complex portal-based solutions, Paubox works natively with your existing email infrastructure. It provides clear, actionable insights into email flow and threat activity, helping you monitor suspicious patterns tied to API abuse or abnormal email forwarding rules.
Paubox reduces reliance on multiple third-party security tools by providing a unified inbound protection layer. This lowers the number of potentially vulnerable integrations and ensures consistent enforcement of security policies.
Paubox’s solution encrypts sensitive emails automatically and silently, maintaining compliance with HIPAA without burdening users. By securing inbound traffic effectively, Paubox strengthens your overall email defense, which is especially important when integration tokens and API keys are targeted.
By protecting your inbound email flow with Paubox, healthcare organizations gain a strong first line of defense against the very exploits that attackers use to compromise email integrations, helping them keep patient data safe and your workflows running smoothly.
See also: HIPAA Compliant Email: The Definitive Guide (2025 Update)
Look for integrations that follow security best practices, request only necessary permissions, undergo regular security audits, and provide transparency about their data handling policies.
Immediately revoke affected credentials or OAuth tokens, audit mailbox rules and access logs, notify your IT/security team, and follow your organization’s incident response plan.
Implement strong email authentication (DMARC, DKIM, SPF), deploy AI-based phishing detection tools, train employees to recognize phishing attempts, and monitor email traffic for suspicious activity.