Vulnerabilities are an important aspect of supers. The traditional "buy disadvantages to gain points to buy advantages" is a model neither Klaxon nor I like at all. For one thing, the disads are always too specific, and for another it tends to produce blind, deaf, socially crippled freaks. Klax went another way.
You and your GM discuss and mutually decide on a vulnerability - not a disadvantage - that ties in with the character concept, including whether or not the character even has a vulnerability. Then, whenever the vulnerability is used in play against the character, she gains a point, which can be accumulated to buy new powers, retcon the character's history, or reboot the character.
Retcon is short for "Retroactive Continuity". This is a device used commonly in comics where the writers selectively ignore something that has happened in the character's historybecause they prefer that it not have happened. By paying the Retcon cost, the player can say "Remember when feeble Aunt May was killed by the Flying Boogeyman? No, you don't, because it never happened. She's been away visiting her younger sister Aunt Elmira, who was sickly. Aunt May is as good as ever!"
Reboot is what happens when the character bites the dust. By paying points equal to the original amount of character points used in chargen, the Reboot cost, the player can create a new character with all the points spent after chargen on new powers, so long as it's a new version of the old character - when the Leaping Leopard dies tragically, saving the city, his offspring/sibling/buddy takes up the cape and cowl to become the new Black Leopard, sion of the glorious departed.