Earlier this year I spent some time delving into Atlassian Confluence to see if I could dig up any bugs that had slipped through the cracks. I wasn't really expecting to turn up much, but I was super excited and surprised when I managed to find an issue within the RSS feed plugin leading to Cross-Site Scripting (XSS) (Twitter: 1, 2; LinkedIn: 1, 2; BugCrowd: 1, 2).
