HTL (HTML Templating Language, formerly known as Sightly) - the Apache Sling XSS-aware template language
HTL (HTML Templating Language, formerly known as Sightly) is an XSS-aware templating language that was introduced in Adobe Experience Manager 6.0 and later donated to Apache Sling. Its distinguishing features are a tight integration with Sling and helping make your HTML immune to cross-site scripting by supplying sensible defaults and anti-XSS filters.