This book constitutes revised selected papers from the refereed conference proceedings of the 11th International Workshop on Socio-Technical Aspects in Security and Trust, STAST 2021, held in conjunction with ESORICS, the European Symposium on Research in Computer Security, as a virtual event, in October 2021.The 10 full papers included in this book were carefully reviewed and selected from 25 submissions. They were organized in topical sections as follows: web and apps; context and modelling; and from the present to the future.