Undocumented features are frequently found in software releases... - dofaq.co
undocumented feature

Undocumented features are frequently found in software releases...

wikipedia - 02 Jul 2015
Undocumented features are frequently found in software releases. Sometimes the documentation is omitted through simple oversight, but undocumented features are often elements of the software not intended for use by end users, but left available for use by the vendor for software support and development.

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