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CISO Briefing: Malicious ‘VS Code’ & Chrome Extensions Are Holding Your PC Hostage. (Your EDR is Blind. Here’s How to Hunt Them.) — by CyberDudeBivash

By CyberDudeBivash · 01 Nov 2025 · cyberdudebivash.com · Intel on cyberbivash.blogspot.com

LinkedIn: ThreatWirecryptobivash.code.blog

BROWSER EXTENSION • INFOSTEALER • EDR BYPASS • SUPPLY CHAIN

Situation: Malicious Chrome & VS Code extensions are the new “Trojan Horse” for APTs (Advanced Persistent Threats). These are not “adware.” They are sophisticated infostealers that bypass your EDR (Endpoint Detection and Response) by “Living off the Land” (LotL) *inside* your “trusted” `chrome.exe` and `vscode.exe` processes.

This is a decision-grade CISO brief. This TTP is the #1 vector for Session Hijacking (MFA Bypass) and Corporate Espionage (stealing AWS/GitHub keys). Your EDR is blind. Your Zero-Trust policy fails. This is a Developer-focused Supply Chain Attack, and we are providing the *only* playbook to hunt and stop it.

TL;DR — Malicious extensions (Chrome, VS Code) on official *and* unofficial marketplaces (Open VSX) are the new “infostealer” backdoor.

• The TTP: “Living off the Trusted Land” (LotL). The malicious extension runs *inside* the “trusted” `chrome.exe` or `vscode.exe` process.
• The “EDR Bypass”: Your EDR is *whitelisted* to *trust* `chrome.exe`. It *cannot* see the malicious code reading your passwords.
• The Impact: This is not a “pop-up ad.” This is a “Hostage” TTP:
  1. Credential Theft: Steals *all* saved browser passwords and credit cards.
  2. Session Hijacking: Steals your *active M365/Salesforce* session cookie, *bypassing MFA*.
  3. IP Theft: Steals your developer’s *AWS, GitHub, and VPN* keys.
• THE ACTION (CISO): 1) AUDIT all installs. 2) HARDEN (Allowlist extensions, block user-writable paths). 3) HUNT for anomalous `chrome.exe` network traffic.
• THE ACTION (User): 1) CHECK your installs (guide below). 2) USE a Password Manager, *not* your browser, to save credentials.

TTP Factbox: Malicious “Trusted Process” Extension

TTP	Component	Severity	Exploitability	Mitigation
Trusted Process Hijack (T1219)	Chrome/VS Code Extensions	Critical	EDR Bypass (LotL)	AppLocker / MDR
Session Hijacking (T1539)	M365/SaaS Cookies	Critical	Bypasses MFA	SessionShield / FIDO2 Keys

Critical Data BreachEDR Bypass TTPMFA Bypass TTPContents

1. Phase 1: The “Trusted” Trojan (Why Your EDR is Blind)
2. Phase 2: The “Hostage” Kill Chain (From Extension to Exfil)
3. Exploit Chain (Engineering)
4. Reproduction & Lab Setup (Safe)
5. Detection & Hunting Playbook (The *New* SOC Mandate)
6. Mitigation & Hardening (The CISO’s 3-Step Plan)
7. Audit Validation (Blue-Team / *User Guide*)
8. Tools We Recommend (Partner Links)
9. CyberDudeBivash Services & Apps
10. FAQ
11. Timeline & Credits
12. References

Phase 1: The “Trusted” Trojan (Why Your EDR is Blind)

As a CISO, you’ve spent millions on a “Next-Gen” EDR (Endpoint Detection and Response) stack. Your vendor promised “AI-powered protection.” Yet, this attack bypasses it completely. Why?

It’s because this attack *never uses a “virus”*. It’s a “Living off the Land” (LotL) attack that exploits your EDR’s *trust*.

1. The “Shadow IT” (The Lure)

Your developer or employee, trying to be productive, goes to the *official* Chrome Web Store or *unofficial* Open VSX marketplace. They install a “helpful” tool: “ChatGPT for Chrome,” “Awesome Code Formatter,” “Productivity Timer.”

2. The “Trusted Process” (The “Bypass”)

The malicious extension is now *part of* `chrome.exe` or `vscode.exe`.
Your EDR sees `chrome.exe` (a *trusted, signed Microsoft/Google process*) running. It *whitelists* it.
The extension’s malicious code (e.g., `background.js`) runs *inside* this trusted process. It has *full access* to everything that process can see.
This is a *fileless attack*. No “malware.exe” is *ever* written to disk. Your EDR, configured to “trust” Chrome, is now 100% blind to the malicious code running inside it.

Phase 2: The “Hostage” Kill Chain (From Extension to Exfil)

This is the full ransomware and espionage kill chain that our Incident Response (IR) teams are seeing in the wild.

Stage 1: Initial Access (The “Phish” or “Shadow IT”)

An attacker uses AI-powered spear-phishing to send a hyper-realistic email to your developer (“Check out this new VS Code AI helper!”), or the developer finds the malicious tool on their own (the “17-Org” TTP).

Stage 2: Execution & Collection (The “Infostealer”)

The user installs the extension. The extension’s code *immediately* runs *inside* the trusted `chrome.exe` or `vscode.exe` process. It *instantly* steals:

• All saved `chrome://settings/passwords` (incl. personal bank, corporate logins)
• All saved `chrome://settings/payments` (all corporate/personal credit cards)
• All *active session cookies* for M365, Salesforce, Google, etc. (This is the MFA Bypass!)
• All developer *secrets* (e.g., `~/.aws/credentials`, `~/.ssh/id_rsa`, `.env` files)

Stage 3: C2 & Data Exfiltration (The “DLP Bypass”)

The malicious extension *bundles* this 4TB of “hostage” data into a JSON payload.
It then makes a “normal” `HTTPS POST` request to an attacker’s C2 server.
Your Firewall/DLP is blind. It sees a “trusted” `chrome.exe` process making a “normal” web connection to `api.cloud-storage.com` and *allows it*.
The breach is complete. The attacker now owns your employee’s *session*, your *IP*, and your *credentials*.

Stage 4: “Holding You Hostage” (The Ransom)

The attacker doesn’t need to *encrypt* your PC. They *own* it.
They use the stolen GitHub/AWS keys to exfiltrate your “crown jewel” source code.
They use the stolen M365 session cookie to *log in as your CEO* (bypassing MFA) and *start a fraudulent wire transfer*.
*This* is the “hostage” situation. They don’t need ransomware; they *are* you.

Exploit Chain (Engineering)

This is a “Trusted Process” Hijack (T1219/T1176). The “exploit” is a *logic* flaw in your Zero-Trust & EDR Whitelisting policy.

• Trigger: User installs a malicious, “typosquatted” extension from an unvetted source (Open VSX) or even the official Chrome store.
• Precondition: EDR/DLP is *whitelisted* to trust all `chrome.exe` / `vscode.exe` / `node.exe` child processes and network traffic.
• Sink (The Breach): The extension’s `background.js` (running as `chrome.exe`) uses `chrome.cookies.get()` and `fetch()` to exfiltrate all session tokens.
• Module/Build: `chrome.exe` → `HTTPS POST [base64_data]` to `attacker-c2.com`.
• Patch Delta: There is no “patch.” The “fix” is MDR (Hunting) + Session Monitoring.

Reproduction & Lab Setup (Safe)

You *must* test if your EDR is blind.

• Harness/Target: A sandboxed Windows 11 VM with your standard EDR agent installed.
• Test: 1) Load a simple “unpacked” Chrome extension. 2) Have its `background.js` read `chrome.cookies.getAll({})`. 3) Have it `fetch()` (POST) this data to a C2 you control (e.g., a “webhook.site” URL).
• Result: Did your EDR/DLP fire a P1 (Critical) alert? Or was it *silent*? If it was silent, *your EDR is blind* to this TTP.

Detection & Hunting Playbook (The *New* SOC Mandate)

Your SOC *must* hunt for this. Your SIEM/EDR is blind to the exploit itself; it can *only* see the *result*. This is your playbook.

• Hunt TTP 1 (The *Real* IOC): “Impossible Travel / Anomalous Session.” This is your P1 alert. The *result* of this attack is a Session Hijack. You *must* hunt your *cloud* logs (M365, AWS, Salesforce) for: “Show me *all* logins (including *session refreshes*) where the *IP address* or *User-Agent* is *anomalous*.”
• Hunt TTP 2 (The C2): “Hunt your firewall/proxy logs. Show me all `chrome.exe` or `vscode.exe` traffic to *newly-registered* or *uncategorized* domains.” (This is the C2).
• Hunt TTP 3 (The “LotL”): “Show me `vscode.exe` or `python.exe` (dev tools) spawning `powershell.exe`.” This is *always* malicious.

The CISO Mandate: You CANNOT trust your EDR.
Your EDR is a “sensor.” It is *not* a “solution.” You *must* have a 24/7 human-led MDR team (like ours) to hunt for these “trusted process” anomalies.
Explore Our 24/7 MDR Service →

Mitigation & Hardening (The CISO’s 3-Step Plan)

This is a DevSecOps failure. This is the fix.

• 1. HARDEN (The “Policy”):
  • Mandate “Allowlisting”: Use GPO/MDM to *block* all Chrome/VS Code extensions *except* for a *pre-vetted* “corporate allowlist.”
  • Block “Shadow IT”: Block `open-vsx.org` at your firewall. It is *unvetted*.
• 2. PROTECT (The “Session”): You *must* assume the token *will* be stolen.
  • Phish-Proof MFA (FIDO2): Hardware Keys *token-bind* the session, making the *stolen cookie useless*. This is the #1 fix.
  • Session Monitoring: Deploy SessionShield. It’s the *only* tool that *behaviorally* detects the *anomalous use* of that stolen session and *kills it*.
• 3. TRAIN (The “Human”):
  • Stop Browser Passwords: *Mandate* Password Managers (like Kaspersky’s). *Starve* the infostealer.
  • Train Devs: Your developers *must* be trained (with Edureka) on Software Supply Chain Risk.

Audit Validation (Blue-Team / *User Guide*)

Run this *today*. This is not a “patch”; it’s an *audit*.

How to Check Your Browser (Chrome/Edge):

1. Type `chrome://extensions` (for Chrome) or `edge://extensions` (for Edge) in your address bar.
2. AUDIT THE LIST: Do you *know* and *trust* 100% of these?
3. CHECK PERMISSIONS: Click “Details” on each one. Does your “Pretty Theme” *really* need “Read and change all your data on all websites”? **If yes, REMOVE IT. It is a spy.**

How to Check Your VS Code:

1. Open VS Code and run: `code –list-extensions`
2. AUDIT THE PUBLISHER: Look at the *publisher* (e.g., `Microsoft`, `Red Hat`). If you see a *random name* or a *typo* (`Microsft`), **UNINSTALL IT NOW.**

Are You “Living off the Land”? Or Just Getting “Owned”?
Your EDR is blind. Your developers are the new perimeter. CyberDudeBivash is the leader in Ransomware & DevSecOps Defense. We are offering a Free 30-Minute Ransomware Readiness Assessment to show you the *exact* gaps in your “Trusted Process” and “Session Hijacking” defenses.

Book Your FREE 30-Min Assessment Now →

Recommended by CyberDudeBivash (Partner Links)

You need a layered defense. Here’s our vetted stack for this specific threat.

Kaspersky Premium / EDR
This is your *sensor* and *prevention* tool. It *blocks* the initial phish/infostealer, and its Password Manager stops you from saving cards/passwords in the browser.Edureka — DevSecOps Training
Train your developers *now* on Software Supply Chain Risk. This is non-negotiable.AliExpress (Hardware Keys)
*Mandate* this for all developers. Get FIDO2/YubiKey-compatible keys. This *token-binds* the session, making the stolen cookie *useless*.

Alibaba Cloud (VDI)
A key mitigation. Use Virtual Desktops (VDI). If the VDI is popped, you *burn it* and re-image. The infostealer is gone in seconds.TurboVPN
Your developers are remote. You *must* secure their connection to your internal network.Rewardful
Run a bug bounty program. Pay white-hats to find flaws *before* APTs do.

CyberDudeBivash Services & Apps

We don’t just report on these threats. We hunt them. We are the “human-in-the-loop” that your automated EDR is missing.

• SessionShield — Our flagship app. This is the *only* solution designed to *behaviorally* detect and *instantly* kill a hijacked M365/GitHub session. It stops the *result* of the breach.
• Managed Detection & Response (MDR): Our 24/7 SOC team becomes your Threat Hunters, watching your EDR logs for these *exact* “VSCode -> C2” TTPs.
• Adversary Simulation (Red Team): This is the *proof*. We will *simulate* this EDR bypass kill chain to show you where you are blind.
• Emergency Incident Response (IR): You found this TTP? Call us. Our 24/7 team will hunt the attacker and eradicate them.
• PhishRadar AI — Stops the phishing attacks that *initiate* the infostealer breach.

Get a Demo of SessionShieldBook Your FREE 30-Min AssessmentSubscribe to ThreatWire

FAQ

Q: What is a Malicious Browser Extension?
A: It’s a “Trojan Horse” that you *willingly* install. It looks like a “Theme” or “Productivity” tool, but it contains malicious code (e.g., `background.js`) that runs *inside* your trusted browser, giving it full access to all your passwords, cookies, and data.

Q: Why doesn’t my EDR/Antivirus block this?
A: Because your EDR is *configured to trust* `chrome.exe` and `vscode.exe`. This is a “Trusted Process” bypass. The malicious code runs *in the memory* of this trusted process. Your EDR has no “bad file” to scan and sees “normal” behavior (a browser connecting to the internet).

Q: How do I check my extensions *right now*?
A: In Chrome/Edge, type `chrome://extensions` in your address bar. *Audit the permissions*. Does your “Theme” extension *really* need “Read all data on all websites”? If yes, **REMOVE IT.**

Q: What is the #1 fix for this *entire class* of attack?
A: Phish-Proof MFA (Hardware Keys). This TTP’s *goal* is Session Hijacking to bypass MFA. Hardware Keys (FIDO2) use “token-binding,” which makes the stolen cookie *cryptographically useless* to the attacker.

Timeline & Credits

This “Malicious Extension” TTP is an active, ongoing campaign by multiple APTs. The “Open VSX” vector is a *new* supply chain risk for developers.
Credit: This analysis is based on active Incident Response engagements by the CyberDudeBivash threat hunting team.

References

• MITRE ATT&CK: T1176 (Browser Extensions)
• MITRE ATT&CK: T1539 (Session Hijacking)
• CyberDudeBivash: SessionShield – The Session Hijacking Defense

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