Parse nested XML inside CDATA
Company: Intersystems
Role: Software Engineer
Category: Software Engineering Fundamentals
Difficulty: medium
Interview Round: Technical Screen
You receive messages in XML. One element contains a **CDATA section**, but the CDATA text itself is **another XML fragment** (i.e., “XML embedded as text”).
Example input:
```xml
<Message>
<Header>
<Id>123</Id>
</Header>
<Payload>
<![CDATA[
<Event>
<Type>Update</Type>
<User id="42">Alice</User>
</Event>
]]>
</Payload>
</Message>
```
**Task:** Explain how you would “remove the CDATA” so that the embedded XML is parsed as real XML and can be processed normally (e.g., transformed to JSON, queried, validated).
Address:
- A robust parsing approach (not regex-based)
- How you would handle whitespace/encoding/escaping
- Failure cases (malformed inner XML, empty payload)
- Security concerns relevant to XML parsing
Quick Answer: This question evaluates understanding of XML parsing and CDATA handling, including embedded-XML extraction, encoding and escaping concerns, error handling for malformed or empty payloads, and related security considerations such as XXE and entity expansion.