According to the image, this isn't related to the actual Avast antivirus program detections (hence why I didn't get an Avast alert), but most likely the browser security app (Avast Online Security) for Chrome.
Unfortunately I don't use the Chrome, nor do I use the Online Security App, so as an Avast User I'm very limited in what I can do.
I also can't see from the image what it is actually triggering this and not speaking French though I get the gist it is about malicious code.
If you know the exact url that is triggering this you could report it:
Reporting a Possible False Positive File or
Website -
https://www.avast.com/false-positive-file-form.php.
You should get a response in a day or two. Explain the circumstances of this alert - e.g. it isn't the Web Shield triggering it), as I have been able to visit without alert. I would suggest giving a link to this topic as it may help to determine exactly what is triggering the alert.