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CODE RED • ZERO-DAY • SANDBOX ESCAPE

Chrome Zero-Day (CVE-2025-2783) Used to Deliver Spyware – Are You at Risk?

By CyberDudeBivash • October 28, 2025 •

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TL;DR: IMMEDIATE ACTION REQUIRED

A critical zero-day sandbox escape (CVE-2025-2783) in Chrome for Windows is being actively exploited.
The attack is a drive-by compromise: clicking a link in a phishing email is enough to infect a vulnerable browser.
The exploit delivers ‘LeetAgent’ spyware, which is linked to Memento Labs (formerly Hacking Team).
**Solution:** All users must **update Chrome to version 134.0.6998.177/.178 or later IMMEDIATELY**.

Disclosure: This is a malware analysis report for security professionals and the general public. It contains affiliate links to security solutions we recommend. Your support helps fund our independent research.

Definitive Guide: Table of Contents

Part 1: The Executive Briefing — A New Era of Commercial Spyware & Zero-Day Exploits

This is a critical, high-impact threat alert. Google has released an emergency, out-of-band security patch for a high-severity zero-day vulnerability in Google Chrome for Windows, **CVE-2025-2783**. This is not a theoretical flaw; it is being actively exploited in the wild in a sophisticated cyber-espionage campaign dubbed **”Operation ForumTroll”** by Kaspersky researchers. The vulnerability, a sandbox escape, is being chained with another exploit to achieve a full system compromise from a simple link click.

For CISOs, this incident is a five-alarm fire for two reasons:

**The Attack:** It’s a drive-by compromise targeting the world’s most popular browser.
**The Attacker:** The malware and TTPs used in the attack have been linked by Kaspersky to tools developed by **Memento Labs**, the Italian company formerly known as the notorious **Hacking Team**. This signifies a dangerous convergence of state-sponsored APT groups with a commercial, for-profit spyware industry, making top-tier offensive tools available to a wider range of actors.

Part 2: The Attack Chain — Inside “Operation ForumTroll”

The attack is a classic, multi-stage APT campaign that leverages a zero-day for its most critical phase.

The Lure: Hyper-Targeted Spear-Phishing

The campaign begins with personalized spear-phishing emails sent to specific targets, primarily in Russia and Belarus. The lures impersonate organizers of a legitimate scientific and expert forum, “Primakov Readings,” inviting the targets to the event. The emails contain short-lived, personalized links to prevent analysis.

The Compromise: A Zero-Click Drive-By

When a victim clicks the link in a vulnerable Chrome browser, they are directed to a malicious website. No further user interaction is required. The website first runs a “validator script” to ensure the victim is a real human and not a security researcher’s sandbox. Once validated, the site deploys a two-stage exploit chain:

An initial, (currently unidentified) exploit to achieve Remote Code Execution (RCE) within the browser’s sandboxed renderer process.
The **CVE-2025-2783** exploit is then used to escape the sandbox and execute code on the underlying Windows operating system with the user’s full privileges.

The Persistence: COM Hijacking

Once the sandbox is escaped, the attackers deploy a loader that achieves persistence through a technique called **COM hijacking**. By overriding a CLSID in the user registry, the malware tricks Windows into loading a malicious DLL (disguised as `twinapi.dll`) every time a legitimate system process or browser runs.

Part 3: Technical Deep Dive — Anatomy of CVE-2025-2783 & the LeetAgent Payload

CVE-2025-2783: The Mojo Sandbox Escape

The technical root cause of the zero-day is a “logical error at the intersection of Google Chrome’s sandbox and the Windows operating system.” Specifically, it’s an “Incorrect handle provided in unspecified circumstances” within **Mojo**, Chrome’s platform-agnostic Inter-Process Communication (IPC) framework. The exploit misuses Windows pseudo-handles (like -1 or -2) to reference the current thread, allowing it to duplicate thread handles across the sandbox boundary. This effectively “tricks” the highly-privileged browser process into executing code provided by the low-privilege, sandboxed renderer process.

The Payload: ‘LeetAgent’ Spyware

The final payload is a sophisticated spyware implant dubbed “LeetAgent.” Its capabilities include:

**Keylogging and Clipboard Monitoring:** Capturing everything the user types and copies.
**File Stealing:** Actively searching for and exfiltrating files with extensions like `.docx`, `.pdf`, and `.xlsx`.
**Shellcode Injection:** Injecting malicious code into other trusted processes.
**Encrypted C2:** Communicating with its command-and-control (C2) server (often hosted on Fastly.net) over HTTPS, using the ChaCha20 algorithm for encryption.
**”leetspeak” Commands:** The C2 commands themselves are reportedly written in “leetspeak” (e.g., `run_sh3ll`) to further obfuscate their purpose.

The ‘Hacking Team’ Connection

Kaspersky researchers found code similarities, as well as shared file paths and persistence mechanisms, between the LeetAgent toolset and **”Dante,”** the new commercial spyware from Memento Labs. Memento Labs is the rebranded version of the infamous Italian spyware vendor **Hacking Team**, which was known for selling its “Remote Control Systems (RCS)” to governments worldwide.

Part 4: The Defender’s Playbook — A Guide to Patching, Hunting, and Hardening

1. PATCH IMMEDIATELY (The Non-Negotiable Fix)

All users of Chrome on Windows must update to version **134.0.6998.177** or later. Users of other Chromium-based browsers (Microsoft Edge, Brave, Opera, Vivaldi) must apply the corresponding updates from their vendors as soon as they are available.

2. Hunt for Compromise (Assume Breach)

Your SOC team must immediately begin hunting for signs of this attack. Key indicators include:

**Suspicious Process Chains:** Hunt for browser processes (`chrome.exe`, `msedge.exe`) spawning anomalous child processes like `cmd.exe` or `powershell.exe`.
**COM Hijacking Persistence:** Audit the Windows Registry for suspicious COM hijacking CLSID overrides.
**Network Traffic:** Monitor for and investigate all outbound traffic to Fastly.net domains that are not known, legitimate services.

3. Long-Term Strategic Defense

This attack proves that a layered, defense-in-depth strategy is essential.

**Endpoint Detection & Response (EDR):** A modern EDR is the only tool that can reliably detect the *behavior* of a sandbox escape and the subsequent persistence techniques.
**Application Isolation:** As recommended by CISA, you should isolate and restrict web browsers from executing code in other ways.
**Zero Trust Access:** Enforce least-privilege principles. A user’s browser should never have the ability to install programs or modify the registry.

Detect the Post-Exploitation Behavior: A modern **XDR platform** is essential for detecting the post-exploit TTPs. It can see that your trusted browser process is behaving maliciously (e.g., COM hijacking) and automatically terminate the attack chain.

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About the Author

CyberDudeBivash is a cybersecurity strategist with 15+ years in malware analysis, zero-day research, and incident response, advising CISOs across APAC. [Last Updated: October 28, 2025]

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