Is this a "legal" URI query?
?query=username=="john_d"
Notice it has == in its value
On the one hand, it's recognized as a sub-delimiter character and hence reserved as per RFC 3986:
reserved = gen-delims / sub-delims
gen-delims = ":" / "/" / "?" / "#" / "[" / "]" / "@"
sub-delims = "!" / "$" / "&" / "'" / "(" / ")" / "*" / "+" / "," / ";" / "="
On the other hand, a similar param value is mentioned in the FIQL draft
http://example.com/feed.atom?query=title==*new*,author==bob*
So should such query params be validated away by application utilities?