Wordpress Issue: Warnings – Url blocked by robots.txt

One day in Google Webmasters I was getting lots of warnings about a URL blocked by robots.txt. Here is the message I get.

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Warnings Url blocked by robots.txt Sitemap contains urls which are blocked by robots.txt. Sitemap: blog.oscarliang.net/post-sitemap.xml Value: https://oscarliang.com/wp-includes/js/tinymce/plugins/wordpress/img/trans.gif

Clearly this trans.gif image file is blocked from google crawlers. But that’s correct, we should be blocking wp-includes folder. The question is, why the hell is google trying to access this image? The only reason could be this image is visible to google, probably in some posts?

Indeed this image was somehow inserted into posts/pages, after removing it, I don’t get the warning anymore. Here is a simple fix, Go to your All posts, search for trans.gif, or whatever image causes the problem. You will find all the posts that have this image inserted (in my case it was just one post). Do the same for pages.