Günter Grass, the Nobel Prize-winning author, has sued Random House over a claim in a new biography that he volunteered to serve in the Nazis’ Waffen SS unit, Agence France-Presse reported yesterday, citing the online edition of the German magazine Der Spiegel. Mr. Grass, right, is seeking an injunction against the publishing house over a phrase in a biography by Michael Jürgs, which reads: “Günter Grass admitted ... that as a 17-year-old he willingly joined the Waffen SS.” Mr. Grass wrote last year in his autobiography “Peeling the Onion” that he was drafted into the Waffen SS in the final months of World War II, an admission for which he was widely condemned because he had kept his Nazi service a secret for more than 60 years while urging other Germans to confront their painful histories.