XSS vulnerability in "children" macro when displaying excerpts

• Create a parent page A with a child page B
• Add an {excerpt} macro to B containing the text <script>alert("Gotcha!");</script>
• Add the {children} macro to page A, with "Show excerpts" checked
• Alert is shown when viewing A

This is currently present on EAC - likely to be in released versions; not tested yet.

Found by dpabst and me during QA