Joomla 3.86 / "k2" v 3.8 / php 3.6.30

Dear
When updating Joomla from 3.85 to 3.86 I started having a problem in the backend inside the

When I opened the "k2" screen in adm (backend), all the texts were there, but invisible, I had to hover over them and select them to see the same ones.

I repeat: All texts are invisible

Has anyone gone through this, do you know which part of joomla can cause this?

Because of this problem, I ended up going back to Joomla 3.85 and the problem disappears, but I would like to be updated and for this I would need to know if there is any specific file that can cause this

Other tools were working to the satisfaction

Anyone have an idea?

I await a possible help
Thank you
Very successful to all
Jose Carlos

Hello Jose,

Unfortunately I cannot verify the issue.
I am using 3.8.6 as well and the issue is not present.
Are you using any other K2 related extensions?

Krikor
Hello!
All right?

Yes I have some extra "K2" plugins
But in the sense of helping, it seems that I have discovered the problem and maybe it is good to let it reported to anyone who has the same problem.

As I have been using Firefox for years, it seems I have discovered that the problem comes from the new Firefor version 59
Suddenly, I noticed that Firefox had updated itself on that day to version 59
I ran several tests with 3 sites and 2 of them ended up returning to Joomla 3.85 and the problem also disappears in Firefox 59

But I left 1 site to use only test with the Firefox version 59 and Joomla 3.86 and I started to test the Browser

So because of that, I was testing the same admin in Chorme, Edge, Opera, Maxthon and I noticed that in none of them did the problem occur, only in Firefox

So I had the idea of ​​doing a dowgrade of Firefox 59 returning to Firefox 58 and then my final surprise, the problem disappeared.

I've even contacted the Firefox team to report what happened and see if they correct the problem.

My apologies

Always available
A big hug
Very Successful
Jose Carlos
Brazil

THANK YOU!
Chances are that without you I would have never found that issue.
I will reproduce it and provide a patch.

Thank you again :)