I doubt it is a security issue. Mainly because the developer, Zulfikar Nore, posts on his website:
As you may have noticed, Fourteen Extended is currently not available for download at WordPress repository.
The code needs re-review and reworked so that it is forward compatible and safe for use going forward.
For more details on this please contact me.
The plugin is available on GitHub for forking and for pull requests – this is a community plugin and anyone can contribute in any which way they can.
On another topic, you will have notice my recent absence which was due to ill health and I’m further delayed by my other bread and butter projects. With this in mind, please be aware that support in the forum both here and at www.remarpro.com will be very limited for sometime. I will however, give as much support as I can fit in and hope to get back the normal level of support I was giving before as soon as possible.
Once again thank you for reading and for your support thus far – much appreciate your understanding.
Zulf.