A flaw was found in python-bleach version 2.1. Affected versions of this package are vulnerable to URI Scheme Restriction Bypass. Attributes that have URI values weren't properly sanitized if the values contained character entities. Using character entities, it was possible to construct a URI value with a scheme that was not allowed that would slide through unsanitized.
Created python-bleach tracking bugs for this issue:
Affects: fedora-26 [bug 1558268]