Please see USN-4661-1 and ann-snapcraft-4-4-4-library-injection-vulnerability-on-built-snaps for details on this security update.
itszn discovered that Snapcraft includes the current directory when configuring LD_LIBRARY_PATH for application commands. If a user were tricked into installing a malicious snap or downloading a malicious library, under certain circumstances an attacker could exploit this to affect strict mode snaps that have access to the library and were launched from the directory containing the library. Thanks itszn for reporting this issue and helping us make Snapcraft better.
The Snapcraft team and the Ubuntu Security team worked together to release a security update for the Snapcraft deb as well as the Snapcraft snap. Thus, we encourage snap publishers to rebuild their snaps using the latest Snapcraft version. Instructions on how to do it can be found in the USN-4661-1 security notice.