OISF suricata-update unsafely deserializes YAML data

Suricata-Update uses the insecure yaml.load() function. Code will be executed if the yaml-file contains lines like:

hello: !!python/object/apply:os.system ['ls -l > /tmp/output']

The vulnerable function can be triggered by "suricata-update list-sources". The locally stored index.yaml will be loaded in this function and the malicious code gets executed.