Iframe allow attribute not working

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The discussion revolves around the issue of the allow attribute not working in iframes on Discourse. santosguillamot initially reported the problem, stating that despite adding various attributes, only src was being rendered. dax suggested adding the iframe URL to the whitelist, but this did not work.

santosguillamot discovered that Discourse only whitelists certain iframe attributes, and including additional attributes, such as height and weight, made the iframe work. However, they wanted to allow all CodeSandbox iframes.

Others, like downey and selfscrum, reported similar issues with iframes being stripped of attributes. Falco explained that, for security reasons, Discourse is strict about allowing HTML attributes from user input. As a workaround, Falco suggested using a custom attribute, like data-my-special-attr, and targeting it with CSS/JS selectors.

The discussion led to a suggestion by codinghorror to allow admins to specify which iframe attributes to allowlist. However, Falco proposed a simpler solution, which was to allow using anything in the allow attribute for already allowed iframes. This change was eventually merged, resolving the issue for users like santosguillamot, selfscrum, cogdog, and gilby.

1

I have added a codesandbox iframe with different attributes but Discourse is just getting the src. Should I change something in Discourse Settings? I have already allowed this iframe and it is showing, but not correctly.

This is the iframe I am trying to add:

<iframe 
  src="https://codesandbox.io/embed/codesandbox-frontity-rnclp?fontsize=14" 
  title="Frontity - Post with recompose" 
  allow="geolocation; microphone; camera; midi; vr; accelerometer; gyroscope; payment; ambient-light-sensor; encrypted-media; usb" 
  style="width:100%; height:500px; border:0; border-radius: 4px; overflow:hidden;" 
  sandbox="allow-modals allow-forms allow-popups allow-scripts allow-same-origin"
></iframe>

But it is just rendering this:

Need_to_integrate_react-stripe-elements_-%F0%9F%A4%97_Dev_Talk___Questions-_Frontity_Community_Forum

So the iframe is not showing correctly:

09
09344×178 5.53 KB

3 Likes
2

It works for me

image

Just to be sure, did you add the iframe url (https://codesandbox.io/embed/codesandbox-frontity-rnclp) in whitelist? If not, search the site setting allowed iframes.

1 Like
3

I have this domain: https://codesandbox.io/. Shouldn’t be enough? I have found this code at Discourse where it whitelists just some iframe attributes:

If I include the attributes height and weight the iframe works fine, but I would like to allow the other attributes too.

Is there a way of allowing all codesandbox iframes? I thought including just the domain it would work.

Thank you!

EDIT:

I have tried adding this url in whitelist but it is not working neither.

3 Likes
4

I am also running into this problem. I would like to add a class on the IFRAME that I am embedding in my policy privacy post, which embeds the privacy tracking settings from our self-hosted Matomo installation. This would allow me to add a better border and some color to differentiate it from the rest of the privacy policy.

Despite having a class="foo" in my IFRAME element, it is being stripped out, apparently by the white-lister code above. Any chance this could be expanded to have a few more attributes allowed?

5

For security we are very strict of what HTML attributes can be rendered in our page when they come from user input.

What you can do to get that is:

<div data-my-special-attr="42">
  <iframe src="http://example.com">
</div>

and then target that with your CSS / JS selector:

div[data-my-special-attr="42"] > iframe {
  border-color: pink;
}
3 Likes
6

Thanks! That worked on both the topic page and the rendered privacy policy special page as well.

Of note if anyone else is trying this, you can’t add a class attribute, you literally need to add an attribute along the lines of data-foo-attr.

1 Like
7

Rafael thanks for the statement, it clarifies my observed behaviour.
I would like to know whether you have any plans of releasing that lock for audio/video attributes of an iframe. Modern browsers manage accessibility quite good for those allowances, and there are increasingly interesting service offerings which would be great to integrate by users but just lack this type of accessibility.
Thanks.

1 Like
8

We are always open to feedback!

It gets easier if we talk about specifics, like what are the exact attributes you want allowlisted and for what services they are necessary.

2 Likes
An iframe in a post reports not HTTPs
9

ok. I especially think about Jam Systems / Jam · GitLab which would need an allow=“microphone *;” parameter to work properly.

10

I am running into same issue attempting to embed an H5P audio recorder; the allow=“microphone *;” option is stripped from the iframe.

What would take to perhaps have an iframe setting to allow allows?

11

Can we allow admins to specify which iframe attributes they want allowlisted?

1 Like
13

This would be useful, but we’d also be happy with the allow attribute being whitelisted for all. We’re currently running into audio playback issues with embedded Apple and Spotify podcast players. As others have mentioned, the issue is that the allow attribute is being stripped, which contains an important encrypted-media directive.

1 Like
Allowed iframes whitelist not working - 'x-frame-options: SAMEORIGIN'
15

Since we are already strict about which domains can be used in iframes, having yet another setting where we set the allow string for each iframe and parsing the weird allow content format seems a bit much for me.

I made a PR that simply allows using anything in the allow attribute for already allowed iframes:

https://github.com/discourse/discourse/pull/17291

What do you think @sam ?

3 Likes
16

Hmm, I guess I am OK with this, I see your logic here, @david any objections?

1 Like
17

This changed was merged @santosguillamot @selfscrum @cogdog @gilby

3 Likes