UPDATE: Apple has since addressed the cause behind the issue in a newer report.
Shortly after several iOS users complained that some of their older deleted photos were reappearing on their iPhones and iPads, Apple has rolled out an update which addresses the issue, with software version number iOS 17.5.1 and iPadOS 17.5.1 for supported iPhones and iPads. As per the official changelog:
This update provides important bug fixes and addresses a rare issue where photos that experienced database corruption could reappear in the Photos library even if they were deleted.
This is undoubtedly a serious privacy issue, as files that were thought to have been erased were somehow still stored and accessible. While it is a good move on Apple’s behalf to patch the issue rather quickly, the Cupertino tech giant hasn’t publicly addressed the matter, which a lot of concerned users view as a breach of personal data to some extent.
The phenomenon was first noticed by a number of users a few days ago, who noted that photos which were deleted have begun to resurface within their device’s photo library. More users eventually came forward with the same issue, prompting some to question why deleted files were somehow retained on their device and iCloud backups, with some images dating as far back as more than a decade ago.
In any case, a statement from Apple clarifying the matter would most likely be appreciated.
Source: Macrumors