PUA:Win32/InstallCore detected by Windows Security

Try the procedure indicated on the page I referenced in my previous message, and if the messages still arrive, do the following:
Download FRST, once downloaded save it to the desktop, then open it and you will see this:

Click on Scan, at the end of the scan you will have three text files on the desktop: FRST, Addition, and Shortcut. Be sure to wait for the messages indicating that the scan is complete, then send these reports to https://pjjoint.malekal.com/, see this tutorial paragraph Send scan reports to pjjoint, then provide the two links generated by Pjoint in your next message.

Nothing serious, it comes from the CCleaner installation file you downloaded, which is located at C:\Users\thetib\Downloads\Programs\ccleaner_5-59-7230_fr_14492.exe. This detection is due to CCleaner including additional software (adware) in the CCleaner installation file.

To remove it, do the following:
Procedure to follow in the order indicated:

1- Open FRST
2 - Copy the entire script that's in the box below:

Start::
CreateRestorePoint:
CloseProcesses:
GroupPolicy: Restriction ? 
GroupPolicy\User: Restriction ? 
C:\Users\thetib\Downloads\Programs\ccleaner_5-59-7230_fr_14492.exe
End::

3- Once the script is copied, click on Fix.

Let the fix complete. Once it is finished, you will be asked to restart your PC. Please do so as soon as prompted, see below.
Then once your computer has restarted:
4- You will have a Fixlog file on your desktop; send it via https://pjjoint.malekal.com/ and then include the link generated by Pjoint in your next message.

The CCleaner file was no longer present in the download folder, so it's a false alert from Windows Defender, see my first message.