7 facts about sandbox attribute • HTML5 iFrame

Learn three facts about the iFrame sandbox attribute. What HTML5 iFrame tag is and how you can use the sandbox attribute.

What is the HTML5 iFrame tag?

Inline Frame allows embedding interactive documents and content from different sources. In advertising, IFrames are used to embed tracking pixels to count user impressions or visits.

Why can iFrame be a problem?

Unfortunately, iFrames are very often used by attackers to extract user information from the website or inject different vulnerabilities like malware.

What is sandbox attribute?

Sandbox attribute allows restricting access to the iFrame content and what iFrame contents is allowed to access website content.

When the sandbox attribute is added to the iFrame tag, by default it will:

• Treat the content as being from a unique origin.
• Prevent form submission.
• Prevent script execution.
• Disable all available API’s.
• Avoid links from targeting other browsing contexts.
• Restrict the content from navigating its top-level browsing context.
• Block automatically triggered features like video autoplay.

We can reduce the restrictions mentioned above by adding additional parameters to the used sandbox attributes:

• allow-same-origin – Allows the iFrame content to be treated as being from the same origin.
• allow-forms – allows sending forms.
• allow-scripts – enables running scripts to run.
• allow-modals – enables to open modal windows.
• allow-popups – enables to open popups.
• allow-top-navigation – allows the iFrame content to navigate its top-level browsing context.

Do browsers support it?

Yes, except Opera Mini.

Why would we like to use it?

To make sure 3rd party resources embedded on your website have restricted or limited access to the website resources.

How to detect if the sandbox attribute makes problems?

If a browser or iFrame scripts try to execute or access restricted resources, you can find this information in the console log.

Google Chrome plugins problems

Chrome plugins have an option to be injected into all iFrames on the currently loaded page. Plugin configuration manifest file defines this behavior.

Some plugins like LastPass require access to iFrames content to check, for example, if no form needs filling login and password.

Links

• Security in Depth: HTML5’s @sandbox
• Chrome Plugins: Specify Frames

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