Writers often use character stupidity as a plot device. In some cases, usually in humorous writing, the character is ditzy (charmingly stupid). That’s fine if that’s what you are writing, but it doesn’t work in most fiction.
Even smart people do stupid things on occasion. We run the yellow light when it’s turning red or open our mouth when we should keep it shut at work or in social situations. Momentary stupidity is common in life, and it can be used sparingly in fiction without the reader rolling her eyes.
Stupidity where the character has a chance to think about what’s she’s doing but does the stupid thing anyway always fails as a plot device. The heroine who has been in hiding for years won’t choose to be at a televised event where she’s likely to appear on camera.
If she does and the mob realizes she’s alive and comes after her, that’s a plot contrivance, and the author has failed.
If, however, she’s on the scene of a horrendous car wreck and is caught on someone’s cell phone camera pulling a child out of a burning car, and that video appears on YouTube or the local news, then the writer has created a legitimate reason for her to be found.
Writer laziness disguised as character stupidity is never acceptable.