It's possible to accidentally post something, or have it swiped by many of the untrusted and untrustworthy applications on a PC or mobile device.
It's even easier to unintentionally include identifying information when intentionally making a post, whether by failing to catch it when submitting, or by including additional images in your online posting.
There are also wholesale uploads people may make automatically, e.g., when backing up content or transferring data between systems. That may end up unsecured or in someone else's hands.
Even very obscure elements may identify a very specific ___location. There's a story of how a woman's ___location was identified by the interior of her hotel room, I believe by the doorknobs. An art piece placed in a remote Utah ___location was geolocated based on elements of the geology, sun angle, and the like, within a few hours. The art piece is discussed in this NPR piece: <https://www.npr.org/2020/11/28/939629355/unraveling-the-myst...> (2020).
I read the "accidentally" as applying to the "identifying" not the "post", although I agree the sentence structure would suggest "accidentally" as a modifier for "post" that makes a lot less sense.
You're being intentionally dense. No, people don't accidentally post pictures but they often do post them with the intention of showing a certain thing, e.g. profile picture, something for sale, something related to hobbies, household repairs, whatever. All of thse are posted with intent to include a certain object but may include background info that the poster did not consider.
