The remote Bitbucket server is affected by a reflected cross-site scripting (XSS) attack vector.
Versions of Bitbucket 4.x, prior to 4.12.1 contain a reflected XSS attack. This flaw exists because the pull request inbox does not validate input before returning it to users. This may allow a context-dependent attacker to create a specially crafted request that would execute arbitrary script code in a user's browser session within the trust relationship between their browser and the server.
Upgrade to Bitbucket version 4.12.1 or later.