What attackers do. Attackers abuse software extensions, such as browser extensions or plugins for editors and other applications, to keep access, steal data or run code. Extensions run with the trust of the host application and can see what the user sees. This serves Persistence.
How to defend. Manage browser and development tool extensions centrally with allowlists, block installation from outside official stores and review permissions requested by approved extensions. Watch for updates that change an extension's behaviour or owner. Inventory installed extensions across endpoints regularly.
Signs to look for. Look for extensions installed outside policy, extensions requesting access to all sites or cookies, sudden permission changes after an update, and extension processes contacting unknown domains. A common gap is having no inventory of extensions at all.