Enabling public signup does not display Captcha

Summary

Currently when public signup is enabled for both JIRA and Service Desk, Captcha is only displayed from JIRA signup page, not from Customer Portal signup page.

Steps to reproduce

1. Go to JIRA Administration -> System -> General Configuration -> Edit Settings
2. Change Mode to Public and CAPTCHA on signup to ON
3. Go to JIRA Administration -> Applications -> JIRA SERVICE DESK -> Configuration -> Turn ON Public signup
4. Sign up a new account from JIRA and then from Customer Portal

Expected behavior

CAPTCHA is displayed on both signup pages.

Actual behavior

CAPTCHA is only displayed on JIRA signup page. It's not available on Customer Portal signup page:

Note

It seems that CAPTCHA on signup from General Configuration only takes effect on JIRA side, not Customer Portal