Serato Cue Storage Format
At least for MP3 files, Serato stores cue points in the ID3 v 2.3 GEOB tags of the music files. Source
The format of this binary blob has been partially documented in this blog post.
https://bugs.launchpad.net/mixxx/+bug/741613
See also serato_database_format.
This is the Mixxx Wiki - 
Mixxx is a free and open-source DJ software.
Manual
Hardware Compatibility
Reporting Bugs
Getting Involved
Contribution Guidelines
Coding Guidelines
Using Git
Developer Guide
Contributing Mappings
Mixxx Controls
MIDI Scripting
Components JS