What is the ruling on attaching hair extensions and connecting them to the remaining hair to cover baldness, after all other treatments have failed, and is this considered among the forbidden forms of hair lengthening (wasl)?

Hair extensions are forbidden due to the reported saying of the Prophet, peace and blessings be upon him: "Allah has cursed the woman who adds artificial hair (to her own hair) and the woman who asks for it to be added." However, it becomes permissible in cases of necessity, especially when treating disfiguring defects like baldness, which a woman might suffer from. In such cases, it is permissible to use pure hair from non-human sources or synthetic hair.