# If something permitted was cooked with something forbidden in a kli sheni after the fact the food is permitted. Some are strict unless there is a case of great loss.<ref>Shulchan Aruch Y.D. 105:2. The Rashba Torat Habayit 1b quotes someone who says that just like a kli sheni doesn't cause [[Bishul]] (Shabbat 40b) it doesn't cause any transference of taste. The Rashba himself disagrees based on Chullin 8a and Chullin 8b. He held that even though a kli sheni doesn't cause bishul it does cause a transference of taste. The Tur 105:2 understands that the Rashba himself would say that a kli sheni could only transfer taste up to a klipah but himself argues that perhaps it transfers taste completely. The Shulchan Aruch Y.D. 105:2 cites the lenient opinion who says that it doesn't transfer taste as well as the Rashba that it transfers taste up to a klipah. He says initially one should be strict for the Rashba. Shach 105:5 and Taz 105:4 cite the Maharshal who holds that a kli sheni can transfer taste completely and advise being strict. Badei Hashulchan 105:39 is strict unless there is a great loss in which case one can rely on Shulchan Aruch. Chachmat Adam 59:6 says that a klipah is necessary unless there is a loss.</ref>
# If something forbidden was cooked in a pot or utensil that was a kli sheni the pot or utensil needs to be koshered. Some poskim hold it doesn't need to be koshered.<ref>Based on the dispute cited above, the utensils that were made non-kosher because of a kli sheni should not require koshering according to the lenient opinion and should require koshering according to the Rashba. Shulchan Aurch 105:2 is initially strict for the Rashba. Therefore, Minchat Yakov 33:6, Rabbi Akiva Eiger 105:6, Badei Hashulchan 105:39, and Horah Brurah 105:28 write that one should be lenient to kosher something that became non-kosher because of a kli sheni unless it is a loss. Yabia Omer OC 3:24:1 implies this as well. His proof is from the Rif Pesachim 8b, Rosh Pesachim 2:7, Shulchan Aruch O.C. 451:5, Tur and Bet Yosef Y.D. 121:3-5 who say that a kli sheni requires koshering.</ref>
===Dvar Gush ===
# The Rama Y.D 94:7 holds that a solid item in a kli sheni is a kli sheni and there's no difference between a solid and a liquid after they landed. Chavot Daat 92:23 cites Minchat Yakov 61:45 writes that even if a dvar gush is like a kli rishon it can't accomplish bishul, so it can't be boleh umaflit kechad.