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/Angular 2

DomSanitizer

Stable Security Risk Class

Security Risk

Calling any of the bypassSecurityTrust... APIs disables Angular's built-in sanitization for the value passed in. Carefully check and audit all values and code paths going into this call. Make sure any user data is appropriately escaped for this security context. For more detail, see the Security Guide.

Class Overview

class DomSanitizer implements Sanitizer {
  sanitize(context: SecurityContext, value: any) : string
  bypassSecurityTrustHtml(value: string) : SafeHtml
  bypassSecurityTrustStyle(value: string) : SafeStyle
  bypassSecurityTrustScript(value: string) : SafeScript
  bypassSecurityTrustUrl(value: string) : SafeUrl
  bypassSecurityTrustResourceUrl(value: string) : SafeResourceUrl
}

Class Description

DomSanitizer helps preventing Cross Site Scripting Security bugs (XSS) by sanitizing values to be safe to use in the different DOM contexts.

For example, when binding a URL in an <a [href]="someValue"> hyperlink, someValue will be sanitized so that an attacker cannot inject e.g. a javascript: URL that would execute code on the website.

In specific situations, it might be necessary to disable sanitization, for example if the application genuinely needs to produce a javascript: style link with a dynamic value in it. Users can bypass security by constructing a value with one of the bypassSecurityTrust... methods, and then binding to that value from the template.

These situations should be very rare, and extraordinary care must be taken to avoid creating a Cross Site Scripting (XSS) security bug!

When using bypassSecurityTrust..., make sure to call the method as early as possible and as close as possible to the source of the value, to make it easy to verify no security bug is created by its use.

It is not required (and not recommended) to bypass security if the value is safe, e.g. a URL that does not start with a suspicious protocol, or an HTML snippet that does not contain dangerous code. The sanitizer leaves safe values intact.

Class Details

sanitize(context: SecurityContext, value: any) : string

Sanitizes a value for use in the given SecurityContext.

If value is trusted for the context, this method will unwrap the contained safe value and use it directly. Otherwise, value will be sanitized to be safe in the given context, for example by replacing URLs that have an unsafe protocol part (such as javascript:). The implementation is responsible to make sure that the value can definitely be safely used in the given context.

bypassSecurityTrustHtml(value: string) : SafeHtml

Bypass security and trust the given value to be safe HTML. Only use this when the bound HTML is unsafe (e.g. contains <script> tags) and the code should be executed. The sanitizer will leave safe HTML intact, so in most situations this method should not be used.