The remote-management module in the (1) Multi Panels, (2) Comfort Panels, and (3) RT Advanced functionality in Siemens SIMATIC WinCC (TIA Portal) before 13 SP1 and in the (4) panels and (5) runtime functionality in SIMATIC WinCC flexible before 2008 SP3 Up7 does not properly encrypt credentials in transit, which makes it easier for remote attackers to determine cleartext credentials by sniffing the network and conducting a decryption attack.
https://ics-cert.us-cert.gov/advisories/ICSA-16-161-02
http://www.siemens.com/innovation/pool/de/forschungsfelder/siemens_security_advisory_ssa-543623.pdf
http://www.siemens.com/cert/pool/cert/siemens_security_advisory_ssa-526760.pdf