A browser-side compromise occurs when malicious activity runs in a user’s browser, often through injected, replaced, or hijacked website code. Unlike a backend breach, it targets the page and the user’s active session. A compromised script may change what the user sees, capture information, or alter actions before they are submitted.
This matters especially for sites where a logged-in browser can trade, approve, or transfer funds. Attackers may abuse a trusted third-party script or another weakness in the site’s delivery chain, causing the browser to execute harmful code with the page’s access. Defenses include carefully reviewing external scripts, limiting their privileges, using integrity controls, and monitoring loaded dependencies. These measures reduce risk but do not, by themselves, establish how any particular compromise occurred.