This article contains spoilers for King in Black #4 by Donny Cates and Ryan Stegman.
Spider-Man has actually been host to two symbiotes - the Venom symbiote and the Enigma Force. Marvel's current King in Black saga has seen Knull, the god of the symbiote, conquer the entire planet Earth - although now the heroes are finally putting up a fight. Given the scale of this epic, it's easy to forget it all started when Peter Parker tried on an alien costume.
Of course, Peter had no idea he was wearing a symbiote. Marvel's most unlucky superhero had suffered something of a fashion disaster when his costume was shredded while he was on an artificially-created planet called Battleworld, and he unwisely headed to an alien device to whip him up a new outfit. He was soon donning a dark, skintight costume dominated by a white arachnid on the chest, and he kept the new look when he returned to Earth - only ditching it when he realized just what he was really dealing with.
But it turns out that isn't the only symbiote Peter Parker has bonded with. King in Black #4 reveals a cosmic power known as the Enigma Force, which transforms its bearers into Captain Universe, is the yin to Knull's yang - a symbiote that stands for light and life rather than darkness and death. And Peter Parker is one of a handful of human beings to bond with the Enigma Force, wielding its infinite power for a brief time against the terrible threat of the Tri-Sentinel. That means Spider-Man has actually been bonded to not one symbiote, but two.
This may actually not be a coincidence; it's interesting to note that King in Black #4 has seen the Enigma Force choose another who has famously been bonded to one of Knull's symbiotes, Eddie Brock, aka Venom. It's possible the Enigma Force deliberately chose heroes who were familiar with the experience of being host to a symbiote, because their minds would be able to handle the tension a little better due to their prior experience. Alternatively, it could also be the Enigma Force is aware of some lasting taint upon the soul caused by bonding with one of Knull's symbiotes for a time, and is consciously choosing to undo that.
Still, this does mean Spider-Man's history books will need to be revised after King in Black. Technically he hasn't starred in just one "Symbiote Saga" any more, but with two - embracing the second when he became Captain Universe for an admittedly brief time.