Assuming a user wants to upgrade to JIRA 5.1.x, he/she would first take a look at this page.

There, in the Before You Start section, it is mentioned:

If you have installed any additional JIRA plugins (i.e. not included with JIRA), please verify that they will be compatible with the version of JIRA you are upgrading to. You can find a plugin's compatibility information from the the plugin's home page on the Atlassian Plugin Exchange. Once you have confirmed the availability of compatible versions, you should upgrade your plugins after successfully upgrading JIRA. This can be done via the 'Plugin Repository' in your Administration Console.

However, in Atlassian Support we still get a lot of upgrade issues coming from incompatible plugins when our friends go for an upgrade. Some of them can be resolved by Atlassian Support, others need to be deflected to the plugin developers as, even though we want to help our friends, it is not possible for us to provide support for a third-party plugin we have no control on.

In that direction, could we perhaps edit the upgrade pages so that the following two points are mentioned:

• Before an upgrade, the JIRA administrators should use the JIRA Update Check (Administration > Plugins > JIRA Update Check) in order to see if some plugins are compatible with the target version or not. (We should make that more obvious as it seems to be missed).
• Regarding the third-party plugins (the ones that are not supported by Atlassian-this should be mentioned in the Atlassian Marketplace) the plugin developers should be contacted instead of Atlassian Support.

The results of this could be two-fold:

1. Customers' time would be saved in the sense that plugins would be checked before the upgrade (sparing them the frustration of things not working)
2. Customers' time would be saved also in the sense of contacting the right person (plugin developers) instead of coming to Atlassian Support and us trying to help, then redirecting them to the third-party plugin developers.

We are here to help our friends in every step of the way. However, perhaps changing our documentation a bit could make more sense and spare them some time.

It seems we actually have everything in this page but it is difficult to find and I don't know how many people would look for it when upgrading.