Hi,
thanks for your rating. I'm sorry that your company policy prevents you from using this add-on.
To clarify first things first: no, this extension does not have any security vulnerabilities or practical security concerns.

Please note that the warning you cite is just a warning of Mozilla that explains the extension is not part of their suggested and extra-strongly vetted add-ons. See https://support.mozilla.org/kb/add-on-badges for more information.
However all add-ons are verified by Mozilla partly in an automated or manual way, see https://extensionworkshop.com/documentation/publish/signing-and-distribution-overview/#post-submission-review for details about that.

Anyway, as for this extension, you can be sure it is not malicious, because you can also check it's source code at https://github.com/rugk/offline-qr-code. Please also note that there are technical measures such as a strict content-security-policy that disallows any outgoing data connections[1] and a strict privacy policy[2].
There is unfortunately nothing I can do about that warning from Mozilla, as it affects all extension that are not specifically selected by Mozilla and reviewed by a small extra team at Mozilla.

The only way to get to be a recommend extension is to convince Mozilla to take this add-on into their program. If you want to do that, please have a look at https://extensionworkshop.com/documentation/publish/recommended-extensions/ and feel free to write Mozilla, as stated there, and suggest and nominate this extension.

Apart from that, if you have any other ideas or issues, feel free to get in touch.
If this helps, it would be glad if you could adjust your voting.

Best regards,
rugk

[1] https://github.com/rugk/offline-qr-code/blob/a0193ba1f1c5f90b06b6e99b9a5973b69d850e21/scripts/manifests/firefox.json#L42
[2] https://addons.mozilla.org/android/addon/offline-qr-code-generator/privacy/

Hi Евлампий and thanks for your rating. I'm sorry that you are apparently having a problem with the extension.

To troubleshoot your problem, we'd need more information about what is actually not working. You should see a QR code button in your browsers toolbar and if you click on it, you should see a QR code. If there continues to be problem, it would be glad if you could open an issue on https://github.com/rugk/awesome-emoji-picker/issues/ and fill out the details there, so we can fix this problem in the next release.

Let us know if this helped by adjusting your voting.

Best regards,
rugk