Open Bug Bounty Community Forum

Hello all 1337[quote][/quote]s,
Am new to this forum and just started my bug hunting. i came across this post https://www.openbugbounty.org/incidents/218697/
and am confused that why the xss is triggered there? Coz i dont see any form there. And what is "d0a" any type of escape sequence ?
can anyone help me to understand this.
thanks.

mod-rewrite rules... ignore it it's only triggering the svg as it's reflected.