event-override

The event-override snippet proxies events and event handlers to defuse events or change their attributes. It works by proxying addEventListener and the original Event class with a CustomEvent class.

Parameters

Name	Description	Mandatory	Default
eventType	The type of the event to target (e.g., click, mouseover, someCustomEvent).	Yes	n.a.
mode	Operation mode: `trusted` (makes `isTrusted` true), `disable` (disables the matching event), or `rewrite` (replaces text inside a string property of the event — see below).	Yes	n.a.
needle	Needle to look for in the event listener function's source — not in the event payload. Enclose in `/` for regex.	No	''
property	The name of the event property to rewrite, for example `data`. Ignored outside `rewrite` mode.	Only in `rewrite` mode	null
pattern	Regex or literal text matched against the property value. Every match is replaced. Ignored outside `rewrite` mode.	Only in `rewrite` mode	null
replacement	The replacement text. Defaults to an empty string, which deletes the matched text. Ignored outside `rewrite` mode.	No	''

rewrite mode

rewrite adjusts the payload a listener reads off an event instead of suppressing the event entirely — useful when defusing the listener would break the page.

Only string values are rewritten. Any other type, and any value that does not match pattern, is passed through untouched.
Every match of pattern inside the value is replaced, not just the first. If the replacement produces no change, the original value is returned as-is.
Rules are matched by property name, so one filter handles one property. If two rewrite filters target the same property on the same event type, the first registered wins.
Both property and pattern are required. If either is missing the snippet logs an error and does nothing.
Leave needle empty unless the string you are matching on actually appears in the listener's own source code. It is tested against the listener, not against the payload, so a token that only exists in the event data will never match it.

Filter examples

Filter	Result
`event-override click disable`	Disables all event listeners for the click event.
`event-override someCustomEvent disable`	Disables all event listeners for the custom event.
`event-override click trusted serveAd`	Makes `isTrusted` true for click events whose listener function matches "serveAd".
`event-override message rewrite '' data /"ads":true/ '"ads":false'`	For every `message` listener, rewrites `"ads":true` to `"ads":false` inside `event.data`.
`event-override message rewrite '' data /trackingId=[^&]*/`	Deletes every `trackingId=...` match from `event.data`. `replacement` is omitted, so matches are removed rather than replaced.

Debugging

Message	When	Definition
`rewrite mode requires the property and pattern params.`	Right after the snippet fires	`mode` is `rewrite` but `property` or `pattern` is missing. The rule is not registered and the snippet does nothing.
`Initialized event-override snippet`	After `addEventListener` has been wrapped	Calls to `addEventListener` are now intercepted. Logged once per page, for the first `event-override` filter.
`Wrapping event listener for <<eventType>>`	A listener matching the event type and needle was registered	That listener will receive the proxied event. If this never appears, either the event type does not match, the `needle` does not match the listener source, or the page registered the listener before the snippet ran.
`Disabling <<eventType>> event`	`disable` mode, a matching listener was registered	The listener was dropped and never reached the native `addEventListener`.
`Providing trusted value for <<eventType>> event`	`trusted` mode, the listener read `isTrusted`	The listener asked for `isTrusted` and got `true`. Only fires when the property is actually read, so a listener that never checks it produces no log.
`Rewriting <<property>> of <<eventType>> event`	`rewrite` mode, the property was read and its value changed	The rewrite happened. If the wrapping message appears but this one never does, the listener either does not read `property`, the value is not a string, or `pattern` is not matching.