S3QL 1.18.1 and earlier uses the pickle Python module unsafely, which allows remote attackers to execute arbitrary code via a crafted serialized object in (1) common.py or (2) local.py in backends/.
https://euvd.enisa.europa.eu/vulnerability/EUVD-2014-0516
https://bitbucket.org/nikratio/s3ql/commits/091ac263809b4e8