Decompression Bomb in Excel file

I have a couple of Excel spreadsheets that run progressively slower and slower, as the file size grows larger and larger.
Checking them with Avast tells me that "Some Files can not be scanned", and upon looking at the details, it says the files are decompression
bombs.

Specifically:
C:\..(filename).xlsx | >xl\drawings\drawing8.xml
C:\..(filename).xlsx | >xl\drawings\drawing9.xml
Is there any way to remove these specific files without destroying or deleting the Excel file? They do not show up in a search of my hard drive.

Solutions to the Problem Decompression Bomb in Excel file

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Rich, do you have some drawings (shapes like rectangles or such perhaps) in the workbook?  I suspect that you do.
I'm not sure how Avast defines a 'decompression bomb'.  But these are probably valid pieces of your Excel file.  Beginning with Excel 2007, an Excel file is not just a one-piece file (as were earlier Excel files), they are actually a big .zip file.
If you have WinZip or 7Zip or a similar tool on your computer, try this.  Create a copy of your .xlsx file to play with (just in case).  Then change the filename from .xlsx (or .xlsm) to .zip.  Open it with WinZip or 7Zip.  Yes, it will!  You're going to
find that at the top level it looks like this:
notice the folder in there named xl  - which is what Avast has pointed you to.  Now if I drill down into that in my simple test file, I see this in that folder:
So you're probably going to see the references to the drawing8/9 files in this area - meaning they are part of the Excel workbook itself.
As a matter of fact, I changed the name back to .xlsx, added a rectangle shape (drawing) to one of the sheets, saved it, renamed it to .zip again and took another look and now I see this:

and inside of that new 'drawings' folder, there's a reference to a file named drawing1.xml which defines my drawing when the file is opened in Excel.
I think Avast has kind of alarmed you over something normal - especially if you know there are drawings in your workbook.
Oh, to return the file back to usable format, just change the .zip back to the original excel file type extension (.xlsx or .xlsm), and you'll be good to go.

Open Action Center by clicking the Start button Picture of the Start button, clicking Control Panel, and then, under System and Security, clicking Review your computer's status.

Update and run your antivirus software. Windows doesn't come with antivirus software, but Action Center can often monitor the antivirus software that you or your computer manufacturer have installed.

Another Safe way to Fix the Problem: Decompression Bomb in Excel file:

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