Back to the CB profile link bug. I saw that the forge-link you gave says "resolved" and "fixed".

Does that mean that a next build of CB will no longer cause this issue if I install it over the current build of CB? Or did I misunderstand?

The ticket is resolved with a merge request created. The fix has not been reviewed and merged yet. Once it has the fix will be available in the next build.

If not, is the fix you created more "permanent" until I get around to migrating to Joomla 3?

Depends on how long you take to migrate to Joomla 3. If this weekend, sure. If in 2 months, no.

And if so, is the fix you created something I would be able to do myself too (just in case) and if yes, how?

If you know how to modify the DOM using your browsers developer console, yes; otherwise, no.

The reason I also ask is because I technically need this link for both the English and the Dutch language (currently the menu item's language is set to "all" and of course I can't change that without editing the menu item).

We ideally should have a new CB build out this week to fix this issue so empty &user= usages in URLs will properly be ignored.

If I understand correctly, then the bug will be fixed when I simply update CB to the newest build in about a week?

Yup

However, I have come across other issues now: new users who register on Joomla can't login even after confirming their account, because their password is denied even if it's entered correctly. This problem only appears if the password contains uppercase letters or numbers, otherwise it works fine. The strange thing is that a password with uppercase does work if it is filled out with lower case (e.g. password Test filled out as test without capital t will actually be accepted). Existing users are not affected, and password changes done by an admin in the backend also work fine - and if the new user changes their password again after that, there is also no problem anymore.

Are they registering through Joomla or CBs registration page? I've never heard of such an issue, sorry. CB doesn't handle encoding the passwords or authenticating them for login as it's all sent through Joomla API. Sounds like maybe a 3rd party Joomla system or user plugin could be altering the passwords maybe.

I fear that a mini-migration to Joomla 3 will become really inevitable and I'll just have to find time to do it.

Unfortunately it is inevitable. Joomla 2.5 is EOL. This means Joomla does not support it anymore. This also means neither do we. CB working on Joomla 2.5 boils down to legacy code and luck, but we do not test Joomla 2.5 at all and likely with CB 2.2 or later we will completely discontinue Joomla 2.5 compatibility (e.g. won't install on Joomla 2.5 anymore). Honestly the best approach for old sites is 1 of the following options.

1. Put in the time and work to update everything (Joomla, CB, installed plugins, 3rd party extensions, etc..)
2. Leave everything as-is (freeze it in time and move on from that site; lock down all admin access to prevent security problems)

Those are basically your only options when dealing with an older site. It is just not possible to update half of it. While CB 2.x tries to continue working in Joomla 2.5 it'll hit a breaking point where it just doesn't work anymore due to odd quirks in Joomla 2.5 behavior (e.g. your issue is done to such quirk.. Joomla 2.5 adds empty URL parameters to menu items).

With that said I don't expect anyone to upgrade their site to the next CMS version as soon as it releases. Give it a few months for extensions to work out some quirks and migration issues. In the case of Joomla 2.5 the last release was like 2 years ago; that's a long time ago and the migration situation will only get worse once Joomla 4.x is released.

I have also asked my server provider for an update of the php version, but they won't do that on the current VPS I'm on, meaning that I will end up having to move the site over to a different server eventually (which I'll probably do after the migration to Joomla 3 is completed).

This would also cause another serious issue in a future CB release (probably CB 2.2). We're dropping support for PHP versions older than 5.6. The reason for this is the API below 5.6 is just not acceptable. We can't maintain up to date 3rd party API libraries either due to PHP 5.3/4 support, which is holding back CBs ability to be stable on PHP 7.1, which brings some massive performance gains and is causing hosts to really push PHP 7.1 to mainstream a lot faster than expected.

In short I encourage everyone to be on Joomla 3.5 and at minimum PHP 5.6 before CB 2.2 arrives as that's likely when we'll be making these requirement changes, but this is still being discussed internally.