Peleus notes that when pulling more than a few RHOSTS targets from the database, MSF writes the intermediate results to a text file instead of leaving them in memory. The aux module check of instantiating a RangeWalker for validation is necessary but insufficient for validating 'file:' RHOSTS specifications.
This clones logic used in the 'check' method in exploit modules to be able to handle file: properly. I suspect this may need to be consolidated and implemented elsewhere tool.
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