Leaflet versions up to and including 1.9.4 are vulnerable to Cross-Site Scripting (XSS) via the bindPopup() method. This method renders user-supplied input as raw HTML without sanitization, allowing attackers to inject arbitrary JavaScript code through event handler attributes (e.g., <img src=x onerror="alert('XSS')">). When a victim views an affected map popup, the malicious script executes in the context of the victim's browser session.