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Introduction: A Trusted Browser Feature Becomes a Dangerous Weapon
Cybercriminals continue to evolve beyond traditional malware techniques, increasingly abusing legitimate system functions to remain hidden from security tools and users alike. Researchers have recently uncovered a sophisticated phishing campaign targeting Windows users through a malicious email attachment disguised as a harmless PDF document. What makes this threat particularly alarming is not the phishing email itself, but the innovative way attackers exploit Google Chrome’s Native Messaging framework to bridge the gap between a browser extension and the underlying Windows operating system.
By leveraging trusted browser functionality, the attackers gain the ability to execute PowerShell commands, steal browser session cookies, collect extensive system information, and maintain remote access while blending into normal browser activity. The campaign highlights a growing cybersecurity trend where threat actors weaponize legitimate software features instead of relying solely on traditional malware techniques.
A Deceptive PDF Attachment Starts the Infection
The attack begins with a carefully crafted phishing email containing what appears to be a PDF invoice attachment. At first glance, the file looks legitimate, displaying a filename similar to a standard document.
However, the attachment actually uses the extension:
Fattura-2819889242.pfd.js
The filename is deliberately designed to trick users into believing they are opening a PDF document. In reality, it is an obfuscated JavaScript file capable of executing malicious code once launched.
After execution, the script silently drops multiple payload files into the Windows temporary directory and initiates a multi-stage infection process. This technique allows attackers to avoid immediate detection while preparing the victim’s system for deeper compromise.
PowerShell Plays a Central Role in the Attack Chain
Once the malicious JavaScript executes, PowerShell becomes one of the primary tools used by the attackers.
The malware launches PowerShell scripts that prepare and deploy a malicious Chrome extension. Instead of requesting normal browser installation permissions, the malware manipulates Chrome policy settings to make the extension appear as if it were installed by an administrator or enterprise management solution.
This approach provides a layer of legitimacy that may prevent users from questioning the extension’s presence while also helping it survive standard browser security checks.
Because PowerShell is a trusted Windows administration tool, many security products may initially view its activity as normal administrative behavior, allowing attackers additional time inside the compromised environment.
The Malicious Chrome Extension Becomes a Surveillance Tool
After installation, the rogue Chrome extension begins harvesting a wide range of information from the victim’s browser.
Researchers observed the extension collecting:
Browser Cookies
Authentication cookies are among the most valuable assets for cybercriminals because they can provide direct access to already authenticated accounts.
Active Tabs and URLs
The malware tracks browsing activity, giving attackers visibility into websites currently being accessed.
Language and Regional Settings
This information helps attackers profile victims and tailor future attacks accordingly.
Browser Fingerprinting Data
Unique device characteristics are gathered to identify systems and maintain persistence.
The stolen information is continuously relayed back to attacker-controlled infrastructure, providing ongoing intelligence about the victim’s activity.
Session Cookie Theft Is More Dangerous Than Password Theft
One of the most concerning capabilities of the malware is its ability to steal authenticated session cookies.
Traditionally, attackers focused on stealing usernames and passwords. However, modern online services often protect accounts using multi-factor authentication (MFA), making stolen credentials less useful.
Session cookies change this equation.
When attackers obtain active authentication cookies, they can effectively inherit an already authenticated session. This allows them to access accounts without needing passwords or MFA codes.
As a result, attackers can potentially gain access to:
Email Accounts
Compromised email access can lead to further account takeovers and identity theft.
Corporate Portals
Business applications protected by MFA may still become vulnerable if session tokens are stolen.
Cloud Services
Attackers can exploit active sessions to access sensitive files and business resources.
Financial Platforms
Authenticated browser sessions may provide direct access to financial data and transactions.
This technique significantly increases the value of browser-focused attacks.
Chrome Native Messaging Becomes the Key Attack Mechanism
The most technically impressive component of the attack is the abuse of Chrome Native Messaging.
Native Messaging is a legitimate Chrome feature designed to allow browser extensions to communicate with approved native applications installed on a user’s computer.
Under normal circumstances, this functionality enables useful integrations between browser-based tools and desktop software.
In this campaign, attackers weaponized the feature.
Rather than directly launching PowerShell from the browser extension, which could trigger security alerts, the extension communicates with a registered native host application.
The communication flow operates as follows:
Step 1: Extension Receives Instructions
The malicious extension receives commands from the
Step 2: Messages Are Passed to Native Host
The extension sends those instructions through Chrome Native Messaging.
Step 3: Native Host Executes Commands
The registered host application launches or interacts with PowerShell on the Windows system.
Step 4: Results Return to the Browser
Collected information is transmitted back through the same communication channel.
This architecture effectively transforms a browser extension into a remote control mechanism for operating system-level activity.
Attackers Can Enumerate Entire Systems
Researchers discovered that operators could use the malware framework to execute various reconnaissance activities.
These include:
File System Discovery
Attackers can inspect directories and files located on the victim’s C: drive.
System Enumeration
Operating system information can be collected to assess the value of a compromised machine.
Remote Command Execution
PowerShell commands can be executed dynamically based on attacker instructions.
Data Collection
Information gathered from both the browser and operating system can be aggregated for later exploitation.
Such capabilities make the threat significantly more dangerous than a simple credential-stealing campaign.
Indicators of Compromise (IOCs)
Malicious Attachment
Fattura-2819889242.pfd.js
Displayed as Fattura-26189991026.pdf
Malicious Files
client_124578.exe
d3d11.dll
Malicious Chrome Extension
Name: Cloud vn105rkj64
ID: gghagmhimhgfeajfdmjkgmmehbokmglg
Associated Domain
ext2[.]info
Organizations should investigate these indicators immediately if observed within their environments.
Deep Analysis: Investigating Native Messaging Abuse Using Linux and Windows Commands
The campaign demonstrates a broader shift toward living-off-the-land techniques.
Attackers increasingly favor legitimate operating system utilities over custom malware.
On Linux systems, analysts can investigate suspicious browser-related processes using:
ps aux | grep chrome
To identify unexpected network connections:
ss -tunap
To locate suspicious files:
find / -name ".js" 2>/dev/null
To inspect active browser-related processes:
top
To review persistence mechanisms:
systemctl list-unit-files
On Windows systems, defenders can inspect PowerShell activity using:
Get-WinEvent -LogName Microsoft-Windows-PowerShell/Operational
To enumerate installed Chrome extensions:
Get-ChildItem "$env:LOCALAPPDATA\Google\Chrome\User Data\Defaultxtensions"
To inspect suspicious processes:
Get-Process
To review network connections:
netstat -ano
To identify unusual scheduled tasks:
schtasks /query /fo LIST /v
Security teams should also monitor Chrome enterprise policies because malware increasingly abuses browser management features to force-install malicious extensions while appearing legitimate.
Native Messaging itself is not inherently dangerous. However, when combined with compromised extensions and PowerShell execution, it creates an effective bridge between browser activity and operating system control.
The campaign illustrates how modern attackers prioritize stealth over complexity. Instead of exploiting browser vulnerabilities, they abuse trusted features that users and security tools often overlook.
This methodology can be highly effective against organizations that focus primarily on signature-based detection. Since PowerShell, Chrome, and Native Messaging are all legitimate components, behavioral monitoring becomes essential.
Defenders should place greater emphasis on extension auditing, browser policy monitoring, PowerShell logging, and session cookie protection.
As browser ecosystems continue to evolve, extensions are increasingly becoming attractive attack surfaces. Organizations that neglect browser security may inadvertently leave a significant blind spot in their defensive posture.
The abuse of session cookies further reinforces the importance of adopting zero-trust principles. Authentication should not rely solely on possession of a valid session token.
Security controls such as device validation, conditional access policies, and continuous authentication can help reduce the effectiveness of cookie theft attacks.
Ultimately, this campaign demonstrates that the browser has become one of the most valuable targets in modern cyber warfare, acting as a gateway to cloud services, enterprise resources, and personal identities.
What Undercode Say:
This attack represents a major evolution in browser-based malware operations because the attackers are not exploiting a vulnerability. Instead, they are abusing intended functionality.
That distinction matters.
Traditional security products are often designed to identify malicious code, exploit chains, suspicious binaries, or unauthorized privilege escalation. In this campaign, nearly every stage leverages legitimate software components.
The phishing attachment is relatively simple.
The true innovation appears after execution.
The attackers understood that Chrome extensions already possess significant access to browsing environments. They also understood that Native Messaging provides an officially supported communication channel between Chrome and local applications.
By combining these capabilities, they effectively transformed Chrome into a remote administration platform.
This creates significant detection challenges.
Many organizations aggressively monitor executable files but rarely inspect browser extensions in depth.
Even fewer organizations continuously monitor browser policy modifications.
The forced installation mechanism is particularly concerning because it mimics enterprise deployment methods commonly used by IT administrators.
A security analyst reviewing the extension may initially assume it was intentionally deployed by the organization.
The use of PowerShell further complicates detection.
PowerShell remains one of the most abused administrative tools in cybersecurity incidents because it exists on nearly every Windows endpoint.
Security teams that lack comprehensive PowerShell logging may never see the malicious activity.
The session cookie theft component is arguably the most valuable capability for attackers.
Modern authentication systems increasingly rely on MFA.
Cybercriminals recognize that stealing passwords alone often no longer guarantees account access.
Stealing authenticated sessions bypasses this obstacle entirely.
This trend has become increasingly visible across both criminal and state-sponsored operations.
The
The extension functions as an intelligence-gathering platform.
The native host functions as a command execution layer.
PowerShell functions as the operating system interaction mechanism.
Each component performs a specific role.
Such separation improves resilience and reduces the likelihood of complete detection.
Another notable aspect is the low dependency on exploits.
No browser vulnerability is required.
No privilege escalation exploit is required.
No kernel-level malware is required.
Everything relies on user interaction and trusted software features.
That makes user awareness a critical defensive layer.
The campaign serves as a reminder that browser security deserves the same attention as endpoint security.
For many users, the browser has become the primary gateway to banking, cloud services, corporate systems, email, and social platforms.
Compromising the browser often provides more value than compromising the operating system itself.
Future variants will likely expand beyond Chrome and target other Chromium-based browsers using similar techniques.
Organizations should therefore view browser extension governance as an essential component of cybersecurity strategy rather than a secondary concern.
✅ Researchers reported a phishing campaign using a fake PDF attachment that actually executes JavaScript-based malware.
✅ Chrome Native Messaging is a legitimate browser feature that allows communication between extensions and native applications, making the described abuse technically plausible.
✅ Session cookie theft can bypass MFA protections by hijacking already authenticated sessions, a technique widely observed in modern cybercrime operations.
Prediction
(+1) Security vendors will increase monitoring of Chrome Native Messaging activity and enterprise browser policies.
(+1) Future endpoint protection platforms will place greater emphasis on browser extension behavior analytics.
(+1) Organizations will adopt stricter browser extension allowlists to reduce attack surfaces.
(-1) Cybercriminal groups will continue abusing legitimate Windows administration tools to avoid detection.
(-1) Browser-focused malware campaigns targeting session cookies will become more frequent across enterprise environments.
(-1) Users who rely solely on MFA without session monitoring may remain vulnerable to account takeover attacks despite strong authentication controls.
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References:
Reported By: www.malwarebytes.com
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