Provide references for CVE-2021-3906.
Where can I find more information about CVE-2021-3906?
References are available at: https://huntr.dev/bounties/f115bdf5-c06b-4627-a6fa-ba6904a43ba3, https://github.com/bookstackapp/bookstack/commit/64937ab826b56d086af9ecea532510d37520ebc8.