Passed this along on the developers forum. Let’s hope that gets this looked at.
Thanks, hopefully it will get resolved. If Avast are only going to distribute version 18.8.2356 people are going to find it hard to get even earlier versions.
Do you mean the high CPU usage?
That is part of it, I have mentioned it in this topic:
https://forum.avast.com/index.php?topic=220639.msg1480638#msg1480638
https://forum.avast.com/index.php?topic=220639.msg1484900#msg1484900
https://forum.avast.com/index.php?topic=220639.msg1486005#msg1486005
Outside of this topic relating to the use of unsecapp.exe by the behaviour shield:
https://forum.avast.com/index.php?topic=223258.msg1484235#msg1484235
Since reverting to avast! free 18.5.2342 on Sunday 18 November 2018 (as the problem first appeared after the 18.6.2349 version update) and I have not experience this problem again and no unsecapp.exe in the Task Manager.
By all accounts simply disabling/stopping the behaviour component also stops the unsecapp.exe appearing in the task manager.
See: https://forum.avast.com/index.php?topic=223258.msg1484236#msg1484236.
Whilst this is another workaround, I would rather have the behaviour shield running and going back was the only way.
So it is a poor choice either going back and having other potential vulnerabilities or disabling the behaviour shield in the latest version and losing its protection.
But the real question is what changed in 18.6.2349 which appears to have the behaviour shield launch unsecapp.exe (with the resultant CPU issue/s) and what is unsecapp.exe doing ?
None of this (behaviour shield changes) appears in the change log, see attached image.
Ah Good to see MartinZ is now on the case.
Take a curiosity: if a person wants to download now the latest version (offline installer) available for Windows xp and Vista now how to do, is there any specific link or the one in your quote is valid?
I believe there are many people interested.
Thank you
Vianello
The Link in his quote goes to where you find all the download links
thank you Pondus,
I have analyzed the downloaded version (offline free version), through the quoted link, it gives me the version 19.x (see attachment)
https://i.postimg.cc/K3g0F5CX/Avast-19-x.png
There is no way to have the link of version 18.8.2356, I think somewhere in the ftp of avast there is, I ask you seen because, if I had problems, already happened in the past, I can perform a version downgrade, moreover, some of my friends would need it in case of PC problems or formatting, and still use windows xp.
@ vianello_85
Unfortunately that is a generic link that will always take you to the latest version of Avast.
It has been mentioned before that there really needs to be an option to get the last version for XP/Vista.
It has also been mentioned that some are experiencing issues with the last version/build for XP?Vista, see my Reply #143 above. Yet not a word from Avast of resolving this, the silence is deafening.
they already said that 19.1 will automatically install 18.8 on XP you don’t need a separate installer
and if your looking for older versions then use https://filehippo.com/download_avast_antivirus/
I believe that is correct. The installer will determine if OS is XP/Vista and install the appropriate version. 
Confirmed. 8) (Note, you’ll need to use the latest online installer…!!)
Thanks for the added info Asyn as I was unaware that the ‘offline’ installer did not offer the same function ???
Thank you all for clarifying my doubts
Vianello
You’re welcome.
I’m already aware of that, the issue is that 18.8 when installed on XP it could cause problems as I have outlined.
I’m fine with looking after myself, I’m more concerned with other XP/Vista users. Whatever is going to be the last versions for XP/Vista should be bulletproof. I’m tired having to band on about this and I’m getting a sore head banging up against the Avast Brick Wall.
My experience is like yours and I feel like you.
After MartinZ Reply #142, I was hopeful that Avast devs may look again at v18 issues. Partcularly as XP users are stuck with no more updates, or in some cases having to use earlier versions as workrounds.
The safest thing would be to update the OS when ever that becomes a possibility.
After upgrading to version 18.8.2356 I’ve noticed that webshield would not run on start up. Had to turn it on manually. I did repair and clean install to no avail.
Started PC in safe mode then went to services then located aswbIDSAgent ,right clicked on properties and selected start up type automatic. This worked for me and solved my predicament. Now everthing is fine once again.