I have a web page that includes an iframe embedding content from WikiSky.
The content from WikiSky largely consists of a bunch of images stitched together into a map of the sky. None of these images have alternate text, ARIA labels, or titles. This makes the content less accessible per WCAG SC 1.1.1.
As the owner/maintainer of the website the iframe appears on, accessibility of my page to my users is important to me. However, I am not the owner/maintainer of WikiSky and as such I don't have the ability to just add alt tags to the source content.
Is there a way to make the third-party content in my iframe more accessible?
I naïvely tried using JavaScript to add alt tags to the images in the iframe. That didn't work (obviously) because using JavaScript to modify the contents of an iframe introduces security risks.
I also looked for solutions involving the iframe element itself. I thought there might be an attribute that could tell screen readers that the content within the iframe has non-accessible images and give an alternate description for the whole iframe, but I have not found such a solution. I do have aria-label and title attributes set on the iframe, but it doesn't seem to completely resolve the issue.
Alternate question: is this even an issue? Running axe on the page raises an issue for each image within the iframe, but my screen reader (Orca) just skips the iframe element entirely.