GTA Online Players Find Secret Alien Mission PC PS4 XBox One 

Apparently the GTA Online's Gunrunning update contained clues about a secret alien mission, which some modders have already unlocked and played. The Gunrunning code suggested that there might be a UFO crash site nearby the Zancudo military base. The modding group Team Guru have already found a way to unlock the mission. This isn't the first time aliens are in GTA V. There is a sequence in GTA V's single-player mode where Michael does drugs and sees aliens that he has to gun down with a huge chain gun.

As you can see, it's not the most thrilling of missions. At least in the state it's in now, the player comes upon a massive, crashed alien ship, with dead scientists in a swamp. There is an alien egg out in the open that the player acquires, at which point a few ETs spawn and must be dealt with. Then the player drives the egg to a bunker to finish the mission. Bear in mind that this mission, if it's real at all, might not be finished, as it was discovered in the game's code and before Rockstar made any mention of it. The new GTA Online alien mission could be the signal of grander plans.

source via Kotaku