https://bugs.documentfoundation.org/show_bug.cgi?id=164411

--- Comment #4 from Adalbert Hanßen <[email protected]> ---
Yesterday I encountered in one of my files a character style
Character_5f_…_5f_style with more than 8000 repetitions of the sequence _5f in
its name. The character style was not used in the file. It had the properties
"inherited from none" and was displayed as a "custom style".

In the past, I always deleted this notorious charcter syle from any document
where I encountered it. But it always re-appeared again after storing and
reloading the file.

This time, the re-creation of this notorious character style happened in 

Version: 25.2.2.1 (X86_64) / LibreOffice Community
Build ID: 38d746d66d9b82fa248a2e90142b9dd3ddd1d6cd
CPU threads: 8; OS: Linux 6.8; UI render: default; VCL: gtk3
Locale: de-DE (de_DE.UTF-8); UI: en-US
Calc: threaded

This bug also appeared in many earlier versions of LibreOffice Writer.

This time I looked closer at this notorious style and I wanted to find out, how
long the name had grown: I copied the name from the character style properties
dialog to the clipboard and from there to a plain ascii file. I was overwhelmed
to see its tremendous length: there were more than 8000 repetitions of the
character sequence "_5f" in it!

Should we not be concerned if a name like this one once causes a memory
overflow? Therefore I urgently wanted to get rid of it. This time I tried
something else: This time I first deleted the strange Character_5f_…_5f_style
from the document. Then I copied the whole content of the document to the
clipboard. Then I closed the LibreOffice session and started a new one while
having the previous content on the clipboard (some 380 pages). Then I pasted
the whole content of my old document from the clipboard to an new document and
stored it.

Since then, I have opened and closed the new document lots of times and added
notes to it. The strange character style did not reappear so far.

I think, a character style with a name of some 24kB length is something
alarming!

I find such strange character types in some other documents - perhaps because
often I want use paragraph styles and character styles which I am used to. So
it happens that I import the whole style sheet from my most used document to
other documents. It looks this might start an infection chain! 

Just as a safety measure from now on I'll search for user defined character
styles defined in any of my documents if they contain a strange style with such
a strange name - not caring for the number of repetitions in it. If I encounter
one, I'll eliminate it by the way which I found now.

The bug which causes such self repeating style names should be found and
eliminated never the less. There still is a DNA probe of it in the attachment
of my initial report of this bug.

BTW: A similar bug was reported in 2019 as
https://bugs.documentfoundation.org/show_bug.cgi?id=125279. The other one has
something self-repeating itself with the sequence _x005F on store - reload
cycles. In the 125179-thread, a cause seems to be some edit ancestry of the
file with Microsoft Word. Since sometimes, I receive and edit *.doc or *.docx
files, I can't exclude that the styles in my file ever had ancestry with styles
which were part of a file which is a descendant from an original Microsoft
office file. Do Microsoft Word files spread hereditary diseases? Or do they
spread something which becomes a hereditary disease once the file or the
stylesheet in it is taken in by LibreOffice?

The thread 125179 was closed by
https://bugs.documentfoundation.org/show_bug.cgi?id=125279#c11. Was this an off
by one remedy which only healed _x005F self repeating sequences, but not _5f
ones? In the other thread there were also discussions about case of the F.

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