IFrameLWCFlowAttributeChangeEvent.js The LWC has an embedded iFrame. I believe that the listenForMessage() reference window.addEventListener() call in my connectedCallback() is really within the this context of the iFrame, not the LWC. Therefore, when I set a value in that callback, I'm setting a different value than the one in the LWC. Which is…

IFrameLWCFlowAttributeChangeEvent.js

import { LightningElement, api, track } from 'lwc';
import { FlowAttributeChangeEvent } from 'lightning/flowSupport';
import pageUrl from '@salesforce/resourceUrl/recaptcha2';
 
export default class GoogleCapatcha extends LightningElement {
    navigateTo;    
    @api result = "undefined";
 
    connectedCallback(){
        var self = this;
        this.navigateTo = pageUrl;
 
        window.addEventListener("message", function(message) {
            self.result = (message.data === "captcha success") ? "true" : "false";
            self.dispatchEvent(new FlowAttributeChangeEvent('result', self.result));
        });
    }
}