hardReflected XSSPro
Kismet
A matchmaker's bio editor only allows six tags. One of them has a surprise.
The Scenario
Kismet is a small-town matchmaking service that still sends real letters. The online bio editor allows a short whitelist of tags for formatting — including <details>, for collapsible sections. The dev knew about markdown. He didn't know about ontoggle.
Challenge Intel
Synopsis
Only six tags are allowed. One of them fires JS when opened.
What It Is
A Sinatra bio preview page with a tight tag whitelist that preserves all attributes.
Who It's For
Someone who can enumerate allowed tags and research HTML event handlers.
Skills You'll Practice
- Whitelist bypass via non-obvious event handlers
- HTML quirks (ontoggle, onanimationend, etc.)
What You'll Gain
- A mental library of exotic events
- Awareness that whitelists preserve attributes too