A NamedNodeMap is a live browser collection that exposes an element’s attributes by name. In the DOM, it is commonly returned when code inspects an element’s attribute set, letting scripts read, add, or remove attributes while the object stays linked to the underlying element.
This matters in cyber security because “live” collections can change during iteration. If a sanitizer loops over a NamedNodeMap and removes attributes from the same element at the same time, the collection may shift and skip entries. An attacker can abuse that kind of logic bug to keep a dangerous attribute alive long enough for the browser to interpret it. Defenders avoid this by copying attributes into a static list before validation, then applying strict allowlists and treating all rendered metadata as untrusted input.