If you are running an old version of WordPress, chances are you might encounter a problem updating to the newest version or when trying to update plugins.

I got this message when trying to update an old site:

"SSL certificate problem: unable to get local issuer certificate"

As far as I can understand from this helpful post the reason is that the WordPress team included a CA certificate check from version 3.7.0 - so this will cause WordPress to complain since you are not verifying the connection in your current version.

 

The fix:

Add these lines of code to the very end (otherwise will break your site) of your wp-config.php file located in your root directory:

add_filter('https_ssl_verify', '__return_false');
add_filter('https_local_ssl_verify', '__return_false');

 

Here is an example of how it should look like:

 

After updating, you should be able to remove these lines of code.

 

Edit: This might be a very common Xammp error. I have read several posts about issues with certificates in Xammp and my problem was also only occuring on my localhost where i run Xammp. Here is a related problem and a general fix