overly trusting and easily deceived
credulous - naive
A person described as ‘credulous’ is thought to be too willing to believe what they are told, even if there is little evidence to support it. Such people are easily tricked or cheated and tend to be looked down on by others who often view them as foolish or naive. We get the opposite meaning by adding the prefix ‘in-’; i.e. ‘incredulous’ - unwilling or unable to believe something.
The election polls showed that few people are credulous enough to believe that party’s propaganda.
The trader managed to con investors out of millions by preying on their credulity with his scheme.
Andrew accepts rather credulously everything he reads on that website. It’s little wonder he’s so ill-informed.