The "Currency" element of a new pledge was not properly validated, which could potentially lead to a cross-site scripting attack.
CiviCRM Versions 5.10.2 and earlier
CiviCRM Version 5.10.3 and 5.7.4
Upgrade to the latest version of CiviCRM
Patrick Figel of Greenpeace for reporting and fixing the issue
security/core#16