Canonical and next links point to a different website–fix by reset indexable

TL;DR Recently we have had some very strange results on our blog. We traced it to an issue in the indexable table. Clearing that table fixes the issue.

1. We first noticed that Wordfence was reporting hack attempts that it was blocking, but where the userid was from a different blog that we operate, but that should have no connection to the site in question. That is, there should not be a normal way for hackers to be attempting to use userid values from the other site. This was a mystery for several weeks.

2. Later we noticed that the home page of our blog had canonical and link tags pointing to the other site. This would lead spiders and bots to traverse the other blog, and would probably explain the mysterious hack attempts.

3. We could not see how to fix the issue. All of the documentation on changing canonical tags starts out with “go to the page” and change the Yoast canonical setting. However, we do not know of any way to “go to the site home page” in the WordPress admin section–you can only go to posts or pages. The site home page is not in the posts or pages. There might be a way to do this, but we could not discover it. If you did go to any site page that you could in the admin, the Yoast canonical field was empty.

4. Just browsing through the Yoast database revealed bogus entries. There were forty some rows in the indexable table that had in their permalink column entries pointing to the other blog property. For example, a permalink that should have had https://www.oursite.net/blog/ instead had https://www.othersite.net/blog/. The domains “oursite” and “othersite” are of course placeholders. Again, a complete mystery how this could happen.

5. I found that the Yoast Test Helper has a feature to reset the indexable table. I used this feature, and the indexable table had all rows removed.

6. After the indexable table was cleared, the canonical and next tags were cleared from the blog home page.

7. As expected, the indexable table was eventually rebuilt. However, there were no permalink values that had any references to the wrong blog.

8. Checking the canonical and next tags on the home page now have the proper values that point to the proper pages in the blog. So the effect of the problem appears to be fixed, but the root cause of what caused the problem is still unknown.

Bottom line: if your blog gets canonical links pointing to a foreign blog, clear the indexable table.

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