Link Keyphrase warning triggered by image description when using Shortcodes Ultimate plugin

[kopyright]

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• I've searched for any related issues and avoided creating a duplicate issue.

Please give us a description of what happened.

I got a post on my website for which Yoast is throwing a “Link Keyphrase” warning.

http://klf.de/home/publication/19-raptures/

The keyphrase on the website linked above is “19 Raptures” (as it appears in the header).

The link within the post has the text “Independent website” (as in ‘the website of the newspaper called The Independent’) and points to the URL https://www.independent.co.uk/arts-entertainment/lifestyle-gurus-odes-to-recovery-1818102.html

Neither share any similiarities with the keyphrase in question other than the blank space character in the keyphrase.

I tried updating the link text to something completely different (and nonsensical) but the link keyphrase warning still triggers. This also still happens when I change the URL the link is pointing at.

The warning only disappears when I change the keyphrase to something different (“Raptures” instead of “19 Raptures” for example).

Please describe what you expected to happen and why.

Since the keyphrase "19 Raptures" does not appear in the link (neither as text nor as URL) I expected this not to happen.

How can we reproduce this behavior?

1. Create a new post named "19 Raptures"
2. Copy and paste the text from the post linked above
3. Set the post's keyphrase to "19 Raptures"

Technical info

• WordPress version:
• Yoast SEO version:

• If relevant, which editor is affected (or editors):

• Classic Editor
• Gutenberg
• Classic Editor plugin

• Which browser is affected (or browsers):

• IE11
• Edge
• Chrome
• Firefox
• Safari

• Relevant plugins in case of a bug:

• Tested with theme:

[kopyright]

Aha! It seems like Yoast itself might not be the culprit in this case but a combination of Yoast and the Shortcodes Ultimate plugin.

What you cannot see from the URL above is that the post also includes a shortcode:

[su_custom_gallery source="media: 2306,2305" link="image" width="140" height="140"]

The shortcode adds the custom gallery you can see at the bottom of the post. The images linked in the gallery include the keyphrase in their captions, description and alt text.

For some reason is seems that Yoast resolves the shortcode to test the generated actual HTML code against the post's keyphrase and recognizes this in the (to-be) links as soon as it is part of the image's description. Keyphrase appearances in the caption and alt text seem to be ignored.

This does not happen when simply adding the images to the post through Wordpress' own "Add Media" button. On the other hand I don't understand why Yoast would consider those links to be outgoing links in the first place, though?