The following obj.conf code instructs sed-request to encode any (<) and (>) characters posted in an HTML form:
Input fn="insert-filter" method="POST" filter="sed-request" sed="s/</\\</g" sed="s/%3c/\\</g" sed="s/%3C/\\</g" sed="s/>/\\>/g" sed="s/%3e/\\>/g" sed="s/%3E/\\>/g"
Because POST bodies are usually URL-encoded, it is important to check for URL-encoded forms when editing POST bodies. %3C is the URL-encoded form of (<) and %3E is the URI-encoded form of (>).