How to fix error: invalid character in entity name in RSS feeds

I use a GitHub action to update my GitHub profile README with my latest blog posts. For over a week the job had been failing, and I ignored it (rookie mistake). It turns out I had broken my RSS feed when I edited some blog post descriptions and used a character that wasn’t valid in XML (referred to as an invalid token).

The error in the GitHub action workflow run wasn’t very helpful, though: “Error: Invalid character in entity name”. 🫠

Luckily, the RSS Feed Validation Service provided by W3C gave a better error report.

This helped me track down the invalid character to an ampersand (&), which I added to a blog post description a week ago to reduce the character count. The resulting invalid description tag in the XML document looked like this:

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I did some further reading on XML and learned that ampersands, and left and right angled brackets (< and >) must be escaped in XML in order for the document to be valid, unless wrapped in a CDATA section. Read more about XML character data and markup on the official W3C docs.