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VAST-2.0-extension-cdata

VAST-2.0-extension-cdata

<Extension> leaf text with XML-sensitive characters should be wrapped in CDATA

WarningSchemaIAB VAST 2.0 §2VAST 2.0 and later (all versions)

Short answer

When an <Extension> carries a leaf text payload containing XML-sensitive characters (&, <, >), wrap it in a CDATA section. JSON blobs and URL-rich vendor data otherwise rely on fragile XML escaping that is easy to get wrong and breaks parsing.

Why this matters in production

This rule is a strong risk signal. Tags with this issue often still parse, but they become brittle across SDKs, SSAI resolvers, and CTV environments. Schema violations tend to create parser disagreement. One system may recover while another drops the tag entirely, which is why these bugs often show up as environment-specific fill loss. Affected scope: VAST 2.0 and later (all versions).

Invalid

<Extension type="vendor">
  {"key":"a&b","u":"https://x?p=1&q=2"}
</Extension>

Valid

<Extension type="vendor">
  <![CDATA[{"key":"a&b","u":"https://x?p=1&q=2"}]]>
</Extension>
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Other Schema rules

VAST-2.0-text-only-elementText-only element contains a child elementVAST-2.0-unknown-attributeElement has an attribute not defined in the VAST specVAST-2.0-inline-unknown-child<InLine> contains an unrecognised child elementVAST-2.0-wrapper-unknown-child<Wrapper> contains an unrecognised child elementVAST-2.0-creatives-unknown-child<Creatives> may only contain <Creative> elementsVAST-2.0-creative-unknown-child<Creative> contains an unrecognised child elementVAST-2.0-linear-unknown-child<Linear> contains an unrecognised child elementVAST-2.0-trackingevents-unknown-child<TrackingEvents> may only contain <Tracking> elements