Authenticity of Du’a When Looking at the Mirror
Question

What is the supplication for looking in the mirror? Is it “O Allah, You have made my physical appearance good, so make my manners and attitude good”?
Praise be to Allah.This hadith was narrated by Ibn as-Sunni in ‘Amal al-Yawm wa’l-Laylah (163) via al-Husayn ibn Abi’s-Sariy: Muhammad ibn al-Fadl told us, from ‘Abd ar-Rahman ibn Ishaq, from an-Nu‘man ibn Sa‘d, from ‘Ali ibn Abi Talib (may Allah be pleased with him), that when the Prophet (blessings and peace of Allah be upon him) saw his face in the mirror, he said: “Praise be to Allah. O Allah, as You have made my physical appearance good, make my manners and attitude good.”
This is a mawdu‘ (fabricated) hadith. Ibn Abi’s-Sariy is a liar; he was classed as such by Abu ‘Urubah and by his brother Muhammad. (See: Tahdhib at-Tahdhib, 2/315)
‘Abd ar-Rahman ibn Ishaq is matruk (rejected); he was rejected by Ahmad and others. (See: al-Mizan, 2/548)
It was also narrated by Abu Ya‘la (2611) and via him by Ibn as-Sunni in ‘Amal al-Yawm wa’l-Laylah (164): ‘Amr ibn Husayn told us: Yahya ibn al-‘Ala told us, from Safwan ibn Sulaym, from ‘Ata ibn Yasar, from Ibn 'Abbas, who said: When the Messenger of Allah (blessings and peace of Allah be upon him) looked in the mirror, he said: “Praise be to Allah Who has made my physical appearance and my manners and attitude good, and has caused to look good in me that which He caused to look bad in others.”
Regarding Yahya ibn al-‘Ala, Ahmad said: He is a liar who fabricates hadiths. (Al-Mizan, 4/397)
Regarding ‘Amr ibn al-Husayn, Abu Hatim said: His reports are worthless, and he is nothing. Ad-Daraqutni said: He is matruk (rejected). (At-Tahdhib, 8/20)
It was also narrated by Abu’sh-Shaykh in Akhlaq an-Nabi (527), and by Abu’l-Husayn al-Bazzaz in Gharaib Malik (161), via Aban ibn Sufyan: Abu Hilal told us, from Hisham ibn ‘Urwah, from his father, from ‘Aishah (may Allah be pleased with her).
Regarding Aban ibn Sufyan, ad- Daraqutni said: He is matruk (rejected). (Mizan al-I‘tidal, 1/7)
It was also narrated by at-Tabarani in al-Awsat (787), and by Ibn as-Sunni in ‘Amal al-Yawm wa’l-Laylah (165) via Salm ibn Qadim, who said: Hashim ibn ‘Isa al-Burri told us, from al-Harith ibn Muslim, from az-Zuhri, from Anas ibn Malik, who said: When the Messenger of Allah (blessings and peace of Allah be upon him) saw his face in the mirror, he said: “Praise be to Allah, Who created me and made my shape good, and gave an image to my face and made it good, and made me one of the Muslims.”
Regarding Hashim ibn ‘Isa, al-‘Aqili said: He is munkar al-hadith (his hadith is odd). (Ad-Du‘afa al-Kabir, 4/343)
Regarding al-Harith ibn Muslim, ad-Daraqutni said: He is majhul (unknown). (Lisan al-Mizan, 2/160)
It was also narrated by al-Bayhaqi in ad-Da‘wat (489) via Maslamah: Hisham ibn ‘Urwah told us, from his father, from ‘Aishah.
Maslamah is the son of Muhammad ath-Thaqafi. Yahya ibn Ma‘in said: He is nothing.
It was also narrated by al-Mirwazi in Zawaid az-Zuhd (1174) via ‘Abdullah ibn al-Muthanna ibn Anas ibn Malik, who said: A man from the family of Anas ibn Malik told me that he heard Anas ibn Malik say: The Messenger of Allah (blessings and peace of Allah be upon him) would pick up the mirror, look in it and say: “Praise be to Allah Who has perfected my creation and made my image good, and has caused to look good in me that which He has caused to look bad in others.”
This is a da‘if (weak) isnad, because the man who is not named is unknown.
It was also narrated by al-Bazzar in his Musnad (7322) via Dawud ibn al-Muhabbir: ‘Abdullah ibn al-Muthanna told us, from Thumamah, from Anas.
Ibn al- Muhabbir is to be rejected and is accused of lying. (See al-Mizan, 2/20)
This hadith has other isnads, all of which are da‘if (weak) and none of them are sahih (sound).
For more about du’a, please see these answers: 121254 , 20176 and 5112 . 
And Allah knows best.