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## 11.3.3 About Using Escaping Syntax in Substitution Strings

Use escaping syntax in substitution strings.

Developers can append an exclamation mark (`!`) followed by a predefined filter name to substitution strings to escape special characters in the substitution value. Output escaping is an important security technique to avoid Cross Site Scripting (XSS) attacks in the browser.

See Also:

Controlling Output Escaping in Substitution Strings

Parent topic: Creating Custom Themes