We had a case where we were setting an HTML title attribute based on a notes field. Handlebars was correctly escaping all the dangerous characters, but left the newlines since those are valid HTML. However, when we did a diff on that code, we noticed that diff-dom was removing the original attribute and appending pieces of the value as attributes.

We went down the rabbit hole and discovered a flaw in one regex in src/diffDOM/virtual/fromString.ts where this regex doesn't play nicely with newlines.

const attrRE = /\s([^'"/\s><]+?)[\s/>]|([^\s=]+)=\s?(".*?"|'.*?')/g

It should probably be updated to:

const attrRE = /\s([^'"/\s><]+?)[\s/>]|([^\s=]+)=\s?("[^"]*"|'[^']*')/g

I don't think this should break anything. I'm happy to put up a PR if you're OK with it.