{
  "family": "extinstaller",
  "sample_count": 2,
  "category": "advanced_threat",
  "description": "Adware:Win32/Extinstaller is a classification for deceptive software components specifically designed to forcibly install unwanted, malicious, or ad-supported browser extensions into Chrome, Firefox, or Edge. It operates as a local privilege escalation and persistence mechanism, ensuring that even if a user deletes the extension from their browser, the local service will simply reinstall it (`T1189`).<br><br><b>Understanding Extinstaller (Browser Hijackers)</b><br>To an end-user, Extinstaller causes a highly frustrating browsing experience: homepages are changed, default search engines are hijacked, and web pages are injected with unwanted advertisements. For a security team, it represents a risk to corporate data, as these forced extensions often monitor all web traffic, capture search queries, and can potentially steal session cookies or credentials (`T1111`).<br><br><b>Execution and Persistence Mechanics</b><br>Extinstaller is typically bundled with freeware or pirated software. Upon execution, it does not rely on the browser's web store. Instead, it interacts directly with the browser's local configuration files or the Windows Registry. For Chrome, it often abuses the `ExtensionInstallForcelist` enterprise policy (`T1562.001`), locking the extension so the user cannot click 'Remove'. It establishes an OS-level persistence mechanism (a Scheduled Task or Registry Run key) (`T1547.001`) that constantly checks if the malicious extension is active and re-injects it if it has been removed.<br><br><b>Indicators of Compromise & Impact</b><br>The primary impact is privacy violation, browser hijacking, and exposure to malvertising. Host-based IoCs include unauthorized modifications to the `HKLM\\Software\\Policies\\Google\\Chrome\\ExtensionInstallForcelist` registry key, the presence of anomalous scheduled tasks running scripts or unknown executables, and the physical presence of unpacked extension files in `%LocalAppData%` outside the normal browser extension directories. Network IoCs involve constant background beaconing to advertising affiliate networks.",
  "cta": "Published by the SystemHelpdesk team.",
  "aliases": [],
  "enrichment_level": "expert-seo",
  "faq": [],
  "faq_count": 0,
  "mitre_attack": [
    "T1189",
    "T1547.001",
    "T1562.001"
  ],
  "cisa_advisory": null,
  "last_updated": "2026-06-09",
  "mitre_attack_detail": [
    {
      "id": "T1562.001",
      "name": "Impair Defenses: Disable or Modify Tools (Abusing browser policies to prevent extension removal)",
      "tactic": "Defense Evasion"
    },
    {
      "id": "T1189",
      "name": "Drive-by Compromise (Initial distribution via software bundling)",
      "tactic": "Initial Access"
    },
    {
      "id": "T1547.001",
      "name": "Boot or Logon Autostart Execution: Registry Run Keys / Startup Folder (Ensuring the reinstall service runs)",
      "tactic": "Persistence"
    }
  ],
  "containment_steps": [
    "Use an enterprise-grade Adware removal tool to locate and destroy the OS-level persistence mechanisms (the 'reinstaller' service).",
    "Manually remove the malicious registry keys enforcing the `ExtensionInstallForcelist` policy in Windows.",
    "Reset the affected web browsers to their default settings to clear out the malicious extension files and restore normal search behavior.",
    "Implement endpoint application control to prevent users from executing unvetted, bundled software installers."
  ],
  "what_to_avoid": [
    "Do not rely solely on removing the extension from within the browser's UI; Extinstaller is designed to defeat this action.",
    "Avoid ignoring adware infections in a corporate environment; malicious extensions can easily capture sensitive web application data."
  ],
  "target_industries": [
    "Global / Opportunistic"
  ],
  "motivation": "Opportunistic",
  "threat_actors": [
    "Unknown / Cybercriminal"
  ],
  "target_geographies": [
    "Global"
  ]
}