Writing Reports: value the real risk
OWASP at the moment is working at the OWASP Testing Guide v4: you can browse the Guide here
In this Chapter it is described how to value the real risk as result of a security assessment. The idea is to create a general methodology to break down the security findings and evaluate the risks with the goal of prioritizing and managing them.
It is presented a table that can easily represent a snapshot of the assessment. This table represents the technical information to deliver to the client, then it is important to present an executive summary for the management.