Press release from Piniform here:
 
 
http://www.piriform.com/news/release-announcements/2017/9/18/security-notification-for-ccleaner-v5336162-and-ccleaner-cloud-v1073191-for-32-bit-windows-users

This compromise only affected customers with the 32-bit version of the v5.33.6162 of CCleaner and the v1.07.3191 of CCleaner Cloud. No other Piriform or CCleaner products were affected.

Who uses 32-bit (x86) anyway?
Edit: Even if I was using the 32-bit (x86) of CCleaner version 5.33.6162 I have already updated and moved to 5.34.6207 a week ago.

rjohnson11
That's why I download software from reputable sources and scan it before installing it. 

It came from a legitimate source, piriform themselves.
I still have the setup backupped, it just sitting there doesn't do any harm, going to check it out later in a virtual machine.
 
Here is a quote:

Based on further analysis, we found that the 5.33.6162 version of CCleaner and the 1.07.3191 version of CCleaner Cloud was illegally modified before it was released to the public, and we started an investigation process.

Source: https://www.piriform.com/news/blog/2017/9/18/security-notification-for-ccleaner-v5336162-and-ccleaner-cloud-v1073191-for-32-bit-windows-users
 

EyeDeeNo
Who uses 32-bit (x86) anyway?
Edit: Even if I was using the 32-bit (x86) of CCleaner version 5.33.6162 I have already updated and moved to 5.34.6207 a week ago.

aka_STEVE_b
I read this but never noticed the part about it being only the 32-bit exe  ......Was worried because I have CCleaner on at least 4-5 systems

The installer ccsetup533.exe is an universal installer that installs 32-bit on a x86 system, but both 32-bit and 64-bit on a x64 system.
So when you install ccsetup533.exe on a x64 windows you also get the 32-bit CCleaner.exe, while normally CCleaner64.exe is used on x64 systems and used by the created shortcut.
 
I'm currently unsure though if running CCleaner.exe on a x64 system does anything, but both the setup and CCleaner.exe will (soon) be detected by AV/Anti malware vendors.
 
Also see:
http://blog.talosintelligence.com/2017/09/avast-distributes-malware.html
https://www.virustotal.com/#/file/1a4a5123d7b2c534cb3e3168f7032cf9ebf38b9a2a97226d0fdb7933cf6030ff/detection (setup)
https://www.virustotal.com/#/file/6f7840c77f99049d788155c1351e1560b62b8ad18ad0e9adda8218b9f432f0a9/detection (CCleaner.exe - 32bit)
 
How to know if you've been affected by the malware:

1. Start up regedit.exe
2. Click on 'Edit' at the top.
3. Click on 'Search'
4. Search for the following text: Agomo

If nothing is found you're not affected by the malware.
If it is found, it should be located here and you're affected: HKEY_LOCAL_MACHINE\SOFTWARE\Piriform
 
Things like these exactly show why we shouldn't blindly trust trusted well-known vendors for always delivering clean files, and that Anti-virus/Anti-malware is still relevant to use, even if they don't catch everything, but like airbags and seatbelts.

Piriform isn't Piriform as we knew it. They sold out to the horrible Avast company.

5.35 update   http://www.piriform.com/news/release-announcements
 
Wednesday, September 20, 2017
 
The Piriform team would like to announce the latest release of CCleaner for Windows.
CCleaner version 5.35 has been released with a new digital signature to update our systems after the September 18th security notification. 
We encourage all users to update to this new version.

Nice thread.

Thanks for posting about this Bobmitch!