WARNING: sanitizing unsafe style value url

Question

I want to set the background image of a DIV in a Component Template in my Angular 2 app. However I keep getting the following warning in my console and I don't get the desired effect... I am unsure if the dynamic CSS background image is being blocked due to security restrictions in Angular2 or if my HTML template is broken.

This is the warning I see in my console (I have changed my img url to /img/path/is/correct.png:

WARNING: sanitizing unsafe style value url(SafeValue must use [property]=binding: /img/path/is/correct.png (see http://g.co/ng/security#xss)) (see http://g.co/ng/security#xss).

The thing is I do sanitize what is injected into my template using the DomSanitizationService in Angular2. Here is my HTML that I have in my template:

<div>
    <div>
        <div class="header"
             *ngIf="image"
             [style.background-image]="'url(' + image + ')'">
        </div>

        <div class="zone">
            <div>
                <div>
                    <h1 [innerHTML]="header"></h1>
                </div>
                <div class="zone__content">
                    <p
                       *ngFor="let contentSegment of content"
                       [innerHTML]="contentSegment"></p>
                </div>
            </div>
        </div>
    </div>
</div>

Here is the component...

Import {
    DomSanitizationService,
    SafeHtml,
    SafeUrl,
    SafeStyle
} from '@angular/platform-browser';

@Component({
               selector: 'example',
               templateUrl: 'src/content/example.component.html'
           })
export class CardComponent implements OnChanges {

    public header:SafeHtml;
    public content:SafeHtml[];
    public image:SafeStyle;
    public isActive:boolean;
    public isExtended:boolean;

    constructor(private sanitization:DomSanitizationService) {
    }

    ngOnChanges():void {
        map(this.element, this);

        function map(element:Card, instance:CardComponent):void {
            if (element) {
                instance.header = instance.sanitization.bypassSecurityTrustHtml(element.header);

                instance.content = _.map(instance.element.content, (input:string):SafeHtml => {
                    return instance.sanitization.bypassSecurityTrustHtml(input);
                });

                if (element.image) {
                    /* Here is the problem... I have also used bypassSecurityTrustUrl */ 
                    instance.image = instance.sanitization.bypassSecurityTrustStyle(element.image);
                } else {
                    instance.image = null;
                }

            }
        }
    }
}

Please note that when I just bound to the template using [src]="image", for example:

<div *ngIf="image">
    <img [src]="image">
</div>

and image was passed using bypassSecurityTrustUrl everything seemed to work well... can anyone see what I am doing wrong?

Answer 1

You have to wrap the entire url statement in the bypassSecurityTrustStyle:

<div class="header" *ngIf="image" [style.background-image]="image"></div>

And have

this.image = this.sanitization.bypassSecurityTrustStyle(`url(${element.image})`);

Otherwise it is not seen as a valid style property