The list is too large to save as a template. The size of a template cannot exceed 52428800 bytes.

By default, you can't save the SharePoint list when it's exceed 52428800 bytes, but you can increase the size by power shell as below:

stsadm -o setproperty -propertyname max-template-document-size -propertyvalue 100000000

Microsoft SharePoint Remote Code Execution Vulnerability

A remote code execution vulnerability exists in Microsoft SharePoint when the software fails to check the source markup of an application package. An attacker who successfully exploited the vulnerability could run arbitrary code in the context of the SharePoint application pool and the SharePoint server farm account.

Remediation:

The security update addresses the vulnerability by correcting how SharePoint checks the source markup of application packages.

Security Updates

Product	Article	Download	Impact	Severity	Supersedence
Microsoft SharePoint Enterprise Server 2016	4462211	Security Update	Remote Code Execution	Critical	4462155
Microsoft SharePoint Foundation 2010 Service Pack 2	4461630	Security Update	Remote Code Execution	Critical	4461580
Microsoft SharePoint Foundation 2013 Service Pack 1	4462143	Security Update	Remote Code Execution	Critical	4461596
Microsoft SharePoint Server 2010 Service Pack 2	4462184	Security Update	Remote Code Execution	Critical
	4461630	Security Update
Microsoft SharePoint Server 2013 Service Pack 1	4462202	Security Update	Remote Code Execution	Critical	4462139
	4462143	Security Update
Microsoft SharePoint Server 2019	4462199	Security Update	Remote Code Execution	Critical	4462171