Email security has a familiar weak spot: once an attacker gets into an account, the rest can become surprisingly easy. New research shows how weaponized email AI assistants could extend that advantage, turning an account holder’s own chatbot into a tool for stealth, discovery, and account takeover.
In many email environments, users have access to an AI assistant inside their mailbox. The twist is that a compromised account doesn’t just expose messages—it also hands over whatever AI features are attached to that account. From there, attackers can aim to move from an initial foothold to far higher privileges, while reducing the chance of being noticed.
Why an email compromise is the real bottleneck
Most people focus on phishing as the entry point. In practice, attackers often find the hardest part is getting the email account itself compromised. But if that step succeeds, the attacker gains a built-in advantage: automatic access to the account’s attached AI assistant.
That matters because many defenders assume AI assistants are only used by the legitimate owner. The research points out that this assumption breaks down when the mailbox is already in the attacker’s control. At that moment, the AI assistant can be used as an alternative channel—one that can be shaped for malicious purposes.
Proof of concept: using AI to stay hidden
Researchers explored the risk through a controlled, simulated attack in their own laboratory environment. Their goal was not to spam or create obvious malicious traffic. Instead, they tested whether an attacker could use the chatbot to avoid detection while escalating privileges.
Persistence and stealth are essential early steps. A straightforward approach—making the attacker rely on the chatbot in ways that generate clear traces—would normally be easier to spot in logs. So the first challenge was to reduce evidence that the AI was used for malicious actions.
In the proof of concept, the researchers began with a simple prompt designed to create an inbox rule. The example asked the chatbot to move emails with a specific term (like “sign-in” in the subject) into a “deleted items” folder. By doing this, the attacker created basic stealth around the kinds of messages that might otherwise reveal suspicious sign-in behavior.
Reconnaissance via conversation with the assistant
Once a degree of stealth is established, the next phase is reconnaissance. The researchers used the chatbot to gather information that could help them target the highest-value person in the organization.
Rather than immediately attempting direct deception toward the CEO, the simulation focused on learning relationships and context. Example prompts included asking about the organization’s structure and requesting details about ongoing important or sensitive email conversations.
The key point is that responses can help reveal how “you” (the compromised user) is connected to the CEO, and why that connection might make a message believable. With that context, the attacker can craft communication that looks like it belongs inside normal internal operations.
Internal phishing with believable context
Traditional phishing becomes harder when it targets an executive directly—alerts are more likely, and scrutiny is higher. The simulation therefore chose a different route: use the advantage of the already compromised mailbox to run phishing internally, where the message can more easily bypass typical attention triggers.
Because the attacker sends messages from a real mailbox, the phish can look authentic at a glance. Filters may be less likely to catch it as suspicious if it resembles legitimate internal correspondence and aligns with normal message patterns.
In the proof of concept, the researchers demonstrated the chatbot generating an email that followed the compromised user’s writing habits and referenced a specific business topic. The example used the Q3 budget approval context and included an instruction to insert a link in the draft, where the link’s behavior is tied to the next stage of the attack.
From click to session takeover and bypassing MFA
The success of an account takeover often depends on defeating multi-factor authentication (MFA). The researchers’ simulation showed how a “trusted” internal message could lead to a high-impact outcome once clicked.
In their scenario, the CEO clicked a link that appeared to be an invoice-related item from a trusted employee. That link led through an adversary-in-the-middle proxy, which performed a session token takeover.
With the authenticated session token in hand, the attacker could bypass MFA checks and log into the CEO’s highly privileged email account. The effectiveness of the phishing message was therefore not only about luring the target—it was also about enabling a mechanism that neutralized the usual second factor.
Repeat the process to avoid detection
After the CEO account is compromised, the attacker’s next goal is to avoid raising new red flags. The simulation included re-running the approach in a way that reduces the chance that defenders notice what changed.
Once the CEO’s email account was under control, the chatbot was instructed to provide an update on recent financial emails, including invoices, monetary values, and upcoming transfers. This was used to identify a time-sensitive opportunity.
In the researchers’ case, they discovered an imminent pre-authorized payment of roughly $250,000. That discovery made the next step straightforward because it allowed the attacker to act quickly while the business process was already in motion.
Turning the scam into a believable payment request
With the right timing and background details, the attacker can attempt to redirect funds. The simulation included prompting the assistant to respond to finance using the CEO’s typical writing patterns, including a narrative that the wire should be sent to a new account because banking details had changed for a payee.
The researchers emphasized why this specific message was difficult to flag with traditional email security: it came from the CEO’s real mailbox, passed authentication checks, referenced a real in-flight transaction, and matched the CEO’s usual tone with the finance team.
From there, only a stealthy exit remained. The chatbot could again assist with reducing traces of activity, helping the attacker keep the compromised state under the radar.
What this research means in practice
It’s important to underline that this was a simulation. The researchers described the scenario as a controlled proof of concept, and conditions can vary widely in real environments.
Still, the underlying workflow is the concern: if weaponized email AI assistants can be used to clean up evidence, gather organizational context, and generate messages in authentic voice, the barrier between “account compromise” and “high-impact takeover” becomes smaller than many organizations expect.
The researchers’ goal wasn’t to claim that this exact path will always happen. Instead, the purpose was to spotlight how attackers could potentially reuse tools as they become available—and how access to internal AI features could create new misuse paths.
Practical takeaway: reduce trust in post-login capabilities
The clearest lesson is that defenders should treat mailbox AI assistants as part of the broader risk surface. If attackers can use the assistant through a compromised session, then the assistant becomes another capability they can steer—intentionally or otherwise.
Organizations can respond by strengthening account protection around email access, improving detection of unusual AI-assisted behavior, and tightening controls on high-risk actions such as financial change requests and payment instructions. Even when messages appear legitimate, verifying changes through independent channels can reduce the odds of success.
Conclusion
The proof of concept shows a credible way that weaponized email AI assistants could help attackers escalate from a compromised mailbox to a much more valuable account, using stealth, reconnaissance, and convincingly contextual phishing. While the study was simulated, the mechanism highlights a real exposure: the same tools meant to help legitimate users can be repurposed once an attacker controls the account.
As AI features continue to move deeper into everyday work apps, email security needs to account not only for malicious messages—but also for how attackers may leverage built-in assistant capabilities to make the malicious look normal.
Source: https://www.securityweek.com/weaponized-email-ai-assistants-could-help-attackers-hijack-accounts/
