I have observed the same behavior when installing Joomla from multiple so called Quick Start Packages embedding themes and plugins. Right now, I have installed, Basic Joomla running on a production server and the same issue persists:
Whenever an article is saved, the content is wrapped within a
<p></p> tag which is visible to end users. So initially you'll write:
But after saving the article, you see:
And if you save it again it becomes:
...and so on.
So if you save the article 10 times, you'll get 10 p tags surrounding the text, and these tags are not source code, they are user-visible.
I initially suspected some plugins; there is the JCE Editor and TinyMCE installed. I disabled TinyMCE, but the behavior persisted. I read somewhere about disabling the surrounding container option in JCE Editor, but it didn't help. So I am not sure that the issue really comes from the editor.
I however also found forum posts about Joomla's Text Filter, so I made sure to disable the text filter but without success: the issue persisted.
Since the issue persists across Joomla reinstalls, I am led to think, that maybe our server environment is the problem, maybe our PHP production settings are causing this, but this gets into the territory of [spam].
We do not normally use the PHP stack, we only set it up to "quickly help" a client get going with a basic project, but boy, this stack is so fragile. Especially when you add CMS in the mix. The issue can be anywhere and you need to go look for Easter Eggs. Nothing to do with Java and its compile time errors and runtime stacktraces in terms of robustness.
But back to the main problem, I do not know where the issue is at this point. We spent about two weeks trying to get the out-the-box experience work. We thought it would be a matter of 2 hours, half a day at most.
Part of this was because of the fragility of PHP mixed with our incompetence with this stack (missing PHP modules, yielding obscure error messages, and since we had no experience we had to hunt), part of this was due the buggy Quick Start Packages that our client insisted to use initially despite our security warning (you do not know the code you are running with these heavily modified, in the age of ransomware, better stick to the official source code), and part of this was due to the issue I am describing in this thread. I even got to the point of wondering if MySQL wasn't somehow adding the tags, but I don't even want to consider the possibility....
Any solution/idea/pointer would be greatly appreciated.
We are running the latest stable Joomla version (3.9.4), with only default plugins, and all of them are updated. But once again, we experienced this problem even with older versions of Joomla shipped with the Quick Start Packages, so I do not think this is a version specific problem.