Pasting Text adds empty space in front

[icc365]

Describe the bug
For the longest time, when I copy and paste text into a paragraph or heading block, it always adds an empty space in front (I added screenshots). Basically, I have to remove that space each time I paste content.

To reproduce
Steps to reproduce the behavior:

1. Create a new page
2. Add a Heading block and paste text into it (don't type it in); or,
3. Add a paragraph block and paste some text into it (don't type it in).
4. After pasting text (which I grabbed some lorem ipsum content), see the space.

Expected behavior
Should be that when pasting text content into a block, there should be no space added in front of the first line (sentence).

Screenshots
I've added a screenshot showing the block editor, source code, and a browser web tools view.

Desktop (please complete the following information):

• OS: Windows 10
• Browser: Chrome
• Version: 79.0.3945.117

Smartphone (please complete the following information):

• Untested in any mobile device

Additional context

• Working Locally on XAMPP, but this also happens on a live site.
• This is an issue I noticed has existed for as long as I can remember when first trying out Gutenberg.
• This is also using WordPress 5.3 and the core block editor (no GB plugin).
  

[icc365]

I've also today noticed that I also get extra spacing on the left and right side of a word when I copy and paste a word to replace another word in a paragraph block. So where there is normal spacing, after selecting a word and then pasting the new word, it adds left and right space.

Seems like pasting things into a block, the editor is adding spaces.

[talldan]

@icc365 This issue was present for a while, but the good news is it's fixed and the fix will be released with WordPress 5.4.

The issue was originally reported in issue #16172 and fixed by #19043.