A previously good working edit form starting adding a backslash ( \ ) before every quotation character ( “ ) after save.

Before Save = src=”file.jpg”

After Save = src=\”file.jpg\”

I discovered the cause was located in a php.ini file (root – public_html)

The cause = magic_quotes

I turned [magic_quotes] OFF  and it stopped adding the backslash

magic_quotes_gpc = On

to

magic_quotes_gpc = Off

Interestingly, I found 2 INI files and had to change both.

I hope it works for you too!