Admittedly, this is pathological, but...
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scala> import net.liftweb.json.JsonAST._
import net.liftweb.json.JsonAST._
scala> import net.liftweb.json.Printer._
import net.liftweb.json.Printer._
scala> compact(render(JField("\"",JObject(List()))))
res0: String = """:{}
scala> compact(render(JString("\"")))
res1: String = "\""
scala> render(JField("\"",JObject(List())))
res2: scala.text.Document = DocCons(DocText(""":),DocCons(DocText({),DocCons(DocNest(2,DocCons(DocBreak,DocNil)),DocCons(DocBreak,DocText(})))))
scala> render(JString("\""))
res3: scala.text.Document = DocText("\"")
I've dug through JsonAST.scala and I can't figure out any way that the quote would be getting through unescaped. JString and JField appear to have the exact same handling, but maybe I'm missing something simple here. This particular value came up in a scalacheck run.