Regarding this narration:
‘Abdullaah ibn Mas‘ood narrated that the Prophet, sallallaahu 'alayhi wa sallam, said, "Indeed, a woman from the wives of the people of Paradise, the whiteness of her shin is visible through seventy garments until her marrow is seen, and that is because Allaah, the Exalted, says: 'As if they are corundum and Marjan.' So as for the corundum, it is a stone, if you were to enter a wire through it and then you polished its cloudiness away, you would surely be able to see it through it."
In tirmidhi, I read this hadith, with another chain, after it:
From ‘Abdullaah ibn Mas‘ood, similar in meaning, and he did not report it in Marfoo‘ form. And this is more correct than the narration of 'Abidah bin Humaid (a narrator in no. 2533), and it has been reported like this by Jarir and more than one from 'Ata' bin As-Sa'ib, and they did not mention it in Marfoo‘ form. [Qutaibah repoted to us (he said): "Jarir reported to us, from 'Ata' bin As-Sa'ib and it is similar to the narration of Abu Al-Ahwas. The companions of 'Ata' did not narrate it in Marfoo‘ form, and this is more correct.] I was wondering, what is being stated as more correct? Is the Mawdhoo‘ narration authentic?

All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad is His slave and Messenger. 

The statement: "This is more correct" was made by At-Tirmithi, and he meant by it that the narration that was narrated by Ibn Mas‘ood, may Allah be pleased with him, (as Mawqoof, i.e. stops at the level of the Companion) is more authentic than the narration that was attributed to the Prophet (as Marfoo‘) whose chain of narrators is weak.

We did not understand what you meant by saying: "Is the Mawdhoo‘ (fabricated) narration authentic?" If you mean the content of the words of Ibn Mas‘ood, then the answer is that although it is confirmed as authentic from the words of Ibn Mas‘ood (Mawqoof), it is something that cannot be said based on the Companion's opinion, so it has the same ruling as Marfoo‘ to the Prophet .

However, if by "Mawdhoo‘ narration", you mean the narration that is said as a lie against the Prophet as per the terminology of the scholars of Hadeeth, then it is not permissible to attribute such a narration to the Prophet and it is not permissible to narrate it except with the purpose of clarifying that it is a lie and fabrication.

Allah knows best.