What should be a boy need to do if he notice a girl's wardrobe malfunction?

Answers :-

a) Generally speaking, if you take someone aside and tell them privately in polite words that their skirt is riding up, pants are riding low, undergarments showing, etc, then that demonstrates that you're concerned for them. Maybe stand in front of them with your back turned to block others from seeing while they take care of things.

Saying things where others can hear, or saying things like, "Hey, I can see your nipples, is that intentional? Thanks!" Or otherwise making a spectacle out of the other person is not cool. The key here is to be subtle and to give them a graceful way to fix it without drawing undue attention.

b) If a boy notices a girl's wardrobe malfunction that she isn't aware of,then he should immediately  talk to her other female friends and notify them about the malfunction. But if he  is comfortable in talking to that girl then he can directly approach the girl and inform her about her clothes.

c) 

1. If you do not know the girl and the malfunction is not harming her in an embarrassing way , then you do not have to do anything , including gossiping, laughing or staring.
2. If you do not know the girl but the malfunction is embarrassing in the crowd , try asking a girl from your group or a known girl to go approach her and tell her nicely, in private and in person.
3. If you know the girl really well, you do the same in private and in person.

d) Well, the problem with INDIAN GIRLS basically is that everything a man does be it good or bad is considered BAD !

So for example, even if you go tell that there's a slight glitch in her outfit - she will conclude the entire scenario into the fact that you were stalking her !

Better not get into the muddle of harsh realities! If there's something wrong with the outfit or if you notice a mere or bad wardrobe malfunction - At this point of the day in our lives - ITS' BETTER YOU IGNORE :)

(PS: I have a friend of mine being accused of false rape allegations since weeks - So, I wouldn't want any other man fall for prey to such problems - Just leave it to the girl - one wrong move and you are taken for the worse )

source :- quora.com