GHSA-438c-3975-5x3f TinyMCE Cross-Site Scripting (XSS) vulnerability in handling iframes

• npm tinymce: < 6.8.1 → fixed in 6.8.1 • NuGet TinyMCE: < 6.8.1 → fixed in 6.8.1 • Packagist tinymce/tinymce: < 6.8.1 → fixed in 6.8.1

Impact A cross-site scripting (XSS) vulnerability was discovered in TinyMCE’s content insertion code. This allowed `iframe` elements containing malicious code to execute when inserted into the editor. These `iframe` elements are restricted in their permissions by same-origin browser protections, but could still trigger operations such as downloading of malicious assets. Fix TinyMCE 6.8.1 introduced a new `sandbox_iframes` boolean option which adds the `sandbox=""` attribute to every `iframe` element by default when enabled. This will prevent cross-origin, and in special cases same-origin, XSS by embedded resources in `iframe` elements. From TinyMCE 7.0.0 onwards the default value of this option is `true`. In TinyMCE 7.0.0 a new `sandbox_iframes_exclusions` option was also added, allowing a list of domains to be specified that should be excluded from having the `sandbox=""` attribute applied when the `sandbox_iframes` option is enabled. By default, this option is set to an array of domains that are provided in embed code by popular websites. To sandbox `iframe` elements from every domain, set this option to `[]`. Workarounds The HTTP Content-Security-Policy (CSP) `frame-src` or `object-src` can be configured to restrict or block the loading of unauthorized URLS. Refer to the TinyMCE Content Security Policy Guide. References • TinyMCE 6.8.1 • TinyMCE 7.0.0