Google has announced that Recaptcha version 1 will be shut down on March 31, 2018. We encourage people who are still using it to upgrade to Recaptcha version 2 (https://www.google.com/recaptcha/intro/) as soon as possible. Recaptcha version 1 will be removed from vBulletin starting in the 5.4.0 release.
We have no current plans to update ReCaptcha on vBulletin 4.2.X.
As of this writing there are reportedly working , free, ReCaptcha 2 add-ons for VB 4.x and 3.x on vBulletin.org though you need to read through the entire threads to get any fixes available for them to work on the latest VB versions like 4.2.5 and 3.8.11.
As always there is no official support for 3rd party add-ons, any support issues should be asked in their respective threads on vBulletin.org, and they are "use at your own risk."
VB 4.x: https://www.vbulletin.org/forum/showthread.php?t=315960
VB 3.x: https://www.vbulletin.org/forum/showthread.php?t=315964
We have no current plans to update ReCaptcha on vBulletin 4.2.X.
As of this writing there are reportedly working , free, ReCaptcha 2 add-ons for VB 4.x and 3.x on vBulletin.org though you need to read through the entire threads to get any fixes available for them to work on the latest VB versions like 4.2.5 and 3.8.11.
As always there is no official support for 3rd party add-ons, any support issues should be asked in their respective threads on vBulletin.org, and they are "use at your own risk."
VB 4.x: https://www.vbulletin.org/forum/showthread.php?t=315960
VB 3.x: https://www.vbulletin.org/forum/showthread.php?t=315964