Siemens SIMATIC S7-1200 CPU devices before 4.0 allow remote attackers to bypass a "user program block" protection mechanism via unspecified vectors.
https://ics-cert.us-cert.gov/advisories/ICSA-16-075-01
https://cert-portal.siemens.com/productcert/pdf/ssa-833048.pdf
http://www.siemens.com/cert/pool/cert/siemens_security_advisory_ssa-833048.pdf