The 2014 Selective Sync bug that permanently deleted users' files
2014
A flaw in Dropbox's desktop Selective Sync feature permanently destroyed the files of users whose client crashed or was force-quit mid-operation — including one photographer who lost more than 8,000 irreplaceable images. Dropbox compensated affected users with a year of Dropbox Pro.
What happened
Selective Sync lets users stop syncing certain folders to a given device to save local disk space. In 2014 it emerged that the feature could do the opposite of saving files: it could obliterate them. The root cause, documented in detail by software engineer Jan Čurn, was an ordering bug — the Dropbox desktop client deleted files locally before it had successfully told the server about the new Selective Sync settings. If the client crashed, hung, or was killed in that window (a common occurrence), the deletions propagated as genuine deletions with no record that anything was wrong.
Čurn used Selective Sync to unsync some photo directories in April 2014; his client froze, he killed and restarted it, and two months later he discovered that 8,343 files — mostly personal photos spanning 2003 to 2014 — were permanently gone. Because he noticed only after Dropbox's deleted-file recovery window had lapsed, his initial support requests were turned away. After he published his account and it spread widely, Dropbox engineers restored a portion of the files (he cited around 1,463) and issued service credit.
In October 2014 Dropbox publicly confirmed the broader bug: a flaw in older desktop app versions could delete files for Selective Sync users, typically after a crash or forced reboot. The company said it was restoring files where it could, shipping fixed clients, blocking the buggy old versions from running, and adding safeguards.
Impact
This is the cardinal sin for a file-sync product: a routine, advertised feature silently and permanently destroyed users' data, with no warning and — past the recovery window — no recourse. The case became one of the most-cited cautionary tales about treating cloud sync as a backup: sync replicates deletions, including buggy ones, everywhere. The photographer's loss in particular turned into a widely shared lesson that even a major, well-funded service can lose your files outright, and that independent backups remain essential.