Is his fasting invalidated if he uncovers his ‘awrah and others see it?

Showing the
‘awrah in front of others for whom it is not permissible to see it is
haraam. It is not permissible for anyone to do that, whether in Ramadaan or
at any other time. It is haraam to uncover it and it is haraam to look at
it. 

It was narrated from Bahz
ibn Hakeem from his father that his grandfather [Mu’aawiyah ibn Haydah
al-Qushayri] (may Allaah be pleased with him) said: I said: O Messenger of
Allaah, with regard to our ‘awrah, what may we uncover of it and what must
we conceal? He said: “Cover your ‘awrah except from your wife and those whom
your right hand possesses (i.e., concubines).” I said, O Messenger of
Allaah, what if a man is with another man? He said, “If you can make sure
that no one sees it, then do not let anyone see it.” I said, O Messenger of
Allaah, what if one of us is alone? He said, “Allaah is more deserving that
you should feel shy before Him than people.” Narrated and classed as hasan
by al-Tirmidhi (2769); narrated by Ibn Maajah (1920); classed as hasan by
al-Albaani in Saheeh al-Tirmidhi.  

It was
narrated from Abu Sa’eed al-Khudri (may Allaah be pleased with him) that the
Messenger of Allaah (peace and blessings of Allaah be upon him) said:
“No man should look at the ‘awrah of another man, and no woman should look
at the ‘awrah of another woman.” Narrated by Muslim, 338. 

Al-Nawawi
(may Allaah have mercy on him) said: This shows that it is haraam for a man
to look at the ‘awrah of another man and for a woman to look at the ‘awrah
of another woman, and there is no difference of opinion concerning that. End
quote. 

Sharh
Muslim, 4/30 

But if the
issue is showing the ‘awrah unintentionally, then there is no sin on you,
and the other person has to avert his gaze and not look at it. 

Fasting is
not invalidated in either case – whether it is done deliberately or by
mistake; in the answer to question no.
38023 we have explained the things
that invalidate the fast. 

In the
answer to question no. 37658 we have explained the effect that sin has on
the fast, and that it reduces the reward, and may erase it altogether. 

And Allaah
knows best.