There is a low severity open redirect vulnerability within affected versions of Bitbucket Data Center. Versions of Bitbucket DC from 8.0.0 to 8.9.12 and 8.19.0 to 8.19.1 are affected by this vulnerability. It is patched in 8.9.13 and 8.19.2.
This open redirect vulnerability, with a CVSS Score of 3.1 and a CVSS Vector of CVSS:3.0/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:N/A:N, allows an unauthenticated attacker to redirect a victim user upon login to Bitbucket Data Center to any arbitrary site which can be utilized for further exploitation which has low impact to confidentiality, no impact to integrity, no impact to availability, and requires user interaction.
Atlassian recommends that Bitbucket Data Center customers upgrade to the version. If you are unable to do so, upgrade your instance to one of the supported fixed versions.