Malware can't execute by itself - you still have to run the file for it be detrimental? True or False? Reasons?
Drive-by Download. https://en.wikipedia.org/wiki/Drive-by_download https://www.asd.gov.au/publications/protect/drive-by_downloads.htm https://www.symantec.com/connect/blogs/drive-download-explained-and-what-you-can-do-about-it https://securingtomorrow.mcafee.com/consumer/family-safety/drive-by-download/ https://heimdalsecurity.com/blog/how-drive-by-download-attacks-work/ https://news.sophos.com/en-us/2014/...f-a-drive-by-download-web-attack-infographic/ ... Etc.
RCE - remote code execution It is more common for web servers and operating systems rather than average consumer software, but sometimes there are some vulnerabilities discovered that can enable RCE exploits.
Exploits can execute Malicious Code by simply accessing an infected webpage, or vulnerable application. Malware is more commonly executed by the user being fooled into executing it through methods of Social Engineering. Exploits more commonly target Government, and Enterprise infrastructure.
Worst of all scenarios is the CCleaner case. This is a perfect example of a Supply chain attack. Note: I got this infection but luckily just the first part of it when it wrote reg entries but my firewall blocked connections to the outside. This saved me from a more harmful stage of the infection.
I think the CCleaner case is more unusual since the installer came from a trusted source. It reminds me of that time Eset discovered saltydog trojan in ComboFix from Bleeping Computer. I was very lucky that I was not infected by the CCleaner malware. I think if I ever get infected (knock on wood) that it will be from an installer from a trusted source. I don't use installers from untrusted sources. Everyone should check the hash of the installer against the known good hash provided by the developer.
Depends on the definition of runs by itself. I assume that includes user initiated indirect methods such as infected Word doc. and the like. However, malware is delivered in stages whereas stage 1 is to install the payload and modify registry run keys, startup locations, or WMI consumer event or scheduled task created. Backdoors also fall in this category. Then there are there are memory based attacks where the payload is downloaded directly into memory and executed from there. Finally the CCleaner incident is really not unique. There have been others in the past; most notably the WannaCry incident.
Depends how it is done: http://www.securityweek.com/google-apps-script-allowed-hackers-automate-malware-downloads
The linked article you provided mentions issues only when editing is involved. In my case no editing will be done, I'm just going to be viewing the mp4 video's after I download them from Google Drive. Should I worry? Here is the quote from the link you supplied: "...attackers uploaded a piece of malware to Google Drive and created a public link to it. They then used Google Docs to send the link to the targeted users. Once victims attempted to edit the Google Docs file, the Apps Script triggers would cause the malware to be automatically downloaded to their devices. "
It depends a bit, if those MP4 files will trigger exploits in the media player then malware can execute automatically. If you're worried about this, then you need to use anti-exploit tools like HMPA. But these tools may sometimes also cause problems with legitimate software. https://www.hitmanpro.com/en-us/alert.aspx