CVE-2021-32708

Flysystem is an open source file storage library for PHP. The whitespace
normalisation using in 1.x and 2.x removes any unicode whitespace. Under
certain specific conditions this could potentially allow a malicious user
to execute code remotely. The conditions are: A user is allowed to supply
the path or filename of an uploaded file, the supplied path or filename is
not checked against unicode chars, the supplied pathname checked against an
extension deny-list, not an allow-list, the supplied path or filename
contains a unicode whitespace char in the extension, the uploaded file is
stored in a directory that allows PHP code to be executed. Given these
conditions are met a user can upload and execute arbitrary code on the
system under attack. The unicode whitespace removal has been replaced with
a rejection (exception). For 1.x users, upgrade to 1.1.4. For 2.x users,
upgrade to 2.1.1.