Release It! Second Edition: about Cross-Site Scripting (page 221)

About “Cross-Site Scripting”:

Cross-site scripting (XSS) happens when a service renders a user’s input directly into HTML without applying input escaping.

I’d prefer “without applying input encoding”.

“escaping” and “encoding” could be used for the same purpose. Even OWASP talks about “encode/escape” in some pages. However, I’d prefer “encoding” because of this reason:

“Writing these encoders is not tremendously difficult, but there are quite a few hidden pitfalls. For example, you might be tempted to use some of the escaping shortcuts like " in JavaScript. However, these values are dangerous and may be misinterpreted by the nested parsers in the browser. You might also forget to escape the escape character, which attackers can use to neutralize your attempts to be safe. OWASP recommends using a security-focused encoding library to make sure these rules are properly implemented.”

Source: Cross Site Scripting Prevention - OWASP Cheat Sheet Series