imapsync 1.564 and earlier performs a release check by default, which sends sensitive information (imapsync, operating system, and Perl version) to the developer's site.

imapsync before 1.584, when running with the --tls option, attempts a cleartext login when a certificate verification failure occurs, which allows remote attackers to obtain credentials by sniffing the network.

imapsync: insecure /tmp usage

imapsync through 2.229 uses predictable paths under /tmp and /var/tmp in its default mode of operation. Both of these are typically world-writable, and thus (for example) an attacker can modify imapsync's cache and overwrite files belonging to the user who runs it.