Vendor email exposure is the quiet leader in incident volume

Vendor email exposure contributes to more healthcare incidents because this form of breach often occurs through administrative and clinical email traffic. Email also appears frequently in breach datasets.

An analysis titled Healthcare Data Breaches: Insights and Implications, processing 3,253 healthcare incidents from 2010–2019, reports 570 email-related breaches, or 17.52% of cases, which is close to paper/films at 17.67% and above network servers at 16.69%. The same study says that breach incidents sped up a lot near the end of the decade, with 457 email instances in the last four years and a high share of about 35% in 2019.

That pattern fits with a larger trend toward hacking and events driven by IT, where phishing and reply-chain exploitation can happen on a large scale but at a low rate. A good way to prevent this is to make the email layer stronger. Paubox is an email security platform that can help find and stop questionable vendor-thread behavior earlier by reporting strange requests, signs of impersonation, and reply-chain manipulation before those messages proliferate.

What does vendor email exposure mean?

Vendor email exposure is the risk that a third-party vendor, partner, or contractor could get into a healthcare delivery organization's email-driven workflows without permission (for example, by stealing credentials or hijacking a session) or by having too much access that no one is watching.

A 2025 study from Research from the Applied Clinical Informatics on third-party access control illustrates how often fundamental governance is not present. Only 51.1% of the 209 healthcare delivery organizations that were polled indicate they have a full list of third parties with network access. Also, 60% admit they don't regularly check who has access to sensitive or private information.

More than half of them also say that a third party broke into their account in the last year, and many of these cases are linked to too much access. Email is a useful way to get into that environment because it's where credentials, links, approvals, and shared documents go. Vendor relationships raise the stakes because attackers can weaponize trusted sender identities, shared mailboxes, and weak authentication to land inside real threads and then pivot into broader access.

How a vendor inbox compromise turns into multiple incidents

Paubox’s 2025 healthcare email security report frames the problem using a set of 180 email-related healthcare breaches and notes three recurring patterns that keep showing up in real incidents. Phishing and credential compromise that leads to mailbox takeover, business email compromise and impersonation, and vendor and business associate email exposure.

In practice, vendor exposure matters because attackers do not need to break a hospital network to cause damage. A hijacked vendor inbox can ride on existing trust and quietly intercept invoices, portal links, authorizations, or shared documents, then pivot into a larger compromise without the loud disruption leaders associate with ransomware.

Paubox’s framing also helps explain why the risk scales. Vendors sit upstream of many organizations at once, and email is the shared workflow layer connecting them, so a single compromised vendor identity can ripple across multiple clients through everyday threads.

Why quiet incidents still hit hard

Quiet healthcare breaches can still create massive problems because they may spread before anyone sees them, and the damage keeps compounding while leaders assume operations are basically normal. Change Healthcare is the clearest example of how a disruption can begin as a vendor-side security incident and then cascade across the entire healthcare ecosystem.

Early reporting described pharmacy and claims disruptions almost immediately after the attack, forcing workarounds and slowing routine care processes long before the full scope of exposure became clear. The longer an incident stays murky, the more downstream organizations burn time on manual workflows, patient communications, payer follow-ups, and exception handling.

News coverage also shows how quiet can still mean massive scale on the data side. Yale New Haven Health reported a hacking incident affecting about 5.6 million people, and the case later moved into an $18 million settlement process, which is a reminder that fallout includes legal spend, monitoring services, and years of trust repair, even when hospitals avoid headline-grabbing shutdowns.

What to do when experiencing a vendor email exposure

Isolating affected mailboxes nd starting incident response to limit lateral movement should all be done right away. Email and authentication logs should be the first things looked at during a forensic analysis because phishing is still a proven way for hackers to get in on a large scale.

A JAMA Network phishing simulation across six hospitals sent 2,971,945 emails and recorded 422,062 clicks, a 14.2% click rate, which supports ongoing simulation and targeted training instead of one-time awareness efforts. Situational prevention also works when it is specific and immediate.

A controlled study published in JAMA Network indicates that warning emails following an initial unauthorized access of PHI are 95% successful in mitigating recidivism, hence endorsing the use of automated notifications in conjunction with monitoring and enforcement. Mandatory privileged access management and anomaly monitoring should be the base of the control set. Paubox Generative AI adds a detection layer by reporting small vendor-thread anomalies like payment redirection language and unexpected authorization requests.

See also: HIPAA Compliant Email: The Definitive Guide (2026 Update)

FAQs

How is vendor email exposure different from a regular phishing attack?

A regular phishing attack goes at your employees directly. Vendor email exposure starts with a trusted partner and then exploits that trusted sender's identity and existing threads to get to your workforce and systems.

What are the most prevalent ways that attackers use email to get into vendor accounts?

Taking over a reply chain, pretending to be a vendor, stealing invoices and payments, making phony secure-message links, and stealing credentials that lead to mailbox takeover.

What numbers suggest that things are getting better over time?

Less time to find vendor problems, fewer exceptions for changing payments, fewer clicks in phishing simulations with vendor themes, and fewer vendors with permanent privileged access.

What is mailbox takeover?

Mailbox compromise is when an attacker gains unauthorized access to an email account and uses it to read messages, steal data, or send convincing emails as the real user.