Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) says: They are both fornicators until they separate.
(b) A narration is also reported from Sayyiduna Ibn Mas'ud (may Allah be pleased with him) that indicates a concession.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13884