  We consider the automatic verification of information flow security policies
of web-based workflows, such as conference submission systems like EasyChair.
Our workflow description language allows for loops, non-deterministic choice,
and an unbounded number of participating agents. The information flow policies
are specified in a temporal logic for hyperproperties. We show that the
verification problem can be reduced to the satisfiability of a formula of
first-order linear-time temporal logic, and provide decidability results for
relevant classes of workflows and specifications. We report on experimental
results obtained with an implementation of our approach on a series of
benchmarks.
