@MarkEWaite May I follow-up on this issue please?
As originally explained, we have several Jenkins controllers. In all but one of them, the Snippet Generator, in certain cases, fails to generate any code and an exception is raised when it is used. I examined all the plugins but could not find an appreciable difference between the working and non-working controllers (expect that the non-working ones use the ActiveDirectory plugin).
However, today I realised that there is a significant difference. The non-working controllers use the Nginx reverse proxy server. The working controller does not. We moved the working system over to Nginx and it, too, no longer works, i.e. the snippet generator fails to generate output and an exception is raised.
I have installed the Strict Crumb Issuer Plugin and, in Configure Global Security > CSRF Protection I have:
Do you think that the Nginx configuration could be causing the problem?
I notice that the exception trace includes:
at hudson.security.csrf.CrumbFilter.doFilter(CrumbFilter.java:154)