Sourced from handlebars's changelog.

v4.5.3 - November 18th, 2019

Bugfixes:

• fix: add "no-prototype-builtins" eslint-rule and fix all occurences - f7f05d7
• fix: add more properties required to be enumerable - 1988878

Chores / Build:

• fix: use !== 0 instead of != 0 - c02b05f
• add chai and dirty-chai and sinon, for cleaner test-assertions and spies,
  deprecate old assertion-methods - 93e284e, 886ba86, 0817dad, 93516a0

Security:

• The properties __proto__, __defineGetter__, __defineSetter__ and __lookupGetter__
  have been added to the list of "properties that must be enumerable".
  If a property by that name is found and not enumerable on its parent,
  it will silently evaluate to undefined. This is done in both the compiled template and the "lookup"-helper.
  This will prevent new Remote-Code-Execution exploits that have been
  published recently.

Compatibility notes:

• Due to the security-fixes. The semantics of the templates using
  __proto__, __defineGetter__, __defineSetter__ and __lookupGetter__ in the respect that those expression now return
  undefined rather than their actual value from the proto.
• The semantics have not changed in cases where the properties are enumerable, as in:

{
  __proto__: 'some string'
}

• The change may be breaking in that respect, but we still only
  increase the patch-version, because the incompatible use-cases
  are not intended, undocumented and far less important than fixing
  Remote-Code-Execution exploits on existing systems.

Commits

v4.5.2 - November 13th, 2019

Bugfixes

• fix: use String(field) in lookup when checking for "constructor" - d541378
• test: add fluent API for testing Handlebars - c2ac79c

Compatibility notes:

• no incompatibility are to be expected

... (truncated)

• c819c8b v4.5.3
• 827c9d0 Update release notes
• f7f05d7 fix: add "no-prototype-builtins" eslint-rule and fix all occurences
• 1988878 fix: add more properties required to be enumerable
• 886ba86 test/chore: add chai/expect and sinon to "runtime"-environment
• 0817dad test: add sinon as global variable to eslint in the specs
• 93516a0 test: add sinon.js for spies, deprecate current assertions
• 93e284e chore: add chai and dirty-chai for better test assertions
• c02b05f fix: use !== 0 instead of != 0
• 8de121d v4.5.2
• Additional commits viewable in compare view

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