Sourced from The npm Advisory Database.

Prototype Pollusion
All versions of handlebars are vulnerable to Prototype Pollusion. Templates may alter an Objects' prototype, thus allowing an attacker to execute arbitrary code on the server.

Affected versions: <=4.0.12

Sourced from handlebars's changelog.

v4.1.0 - February 7th, 2019

New Features

• import TypeScript typings - 27ac1ee

Security fixes:

• disallow access to the constructor in templates to prevent RCE - 42841c4, #1495

Housekeeping

• chore: fix components/handlebars package.json and auto-update on release - bacd473
• chore: Use node 10 to build handlebars - 78dd89c
• chore/doc: Add more release docs - 6b87c21

Compatibility notes:

Access to class constructors (i.e. ({}).constructor) is now prohibited to prevent
Remote Code Execution. This means that following construct will no work anymore:

class SomeClass {
}

SomeClass.staticProperty = 'static'

var template = Handlebars.compile('{{constructor.staticProperty}}');
document.getElementById('output').innerHTML = template(new SomeClass());
// expected: 'static', but now this is empty.

This kind of access is not the intended use of Handlebars and leads to the vulnerability described in #1495. We will not increase the major version, because such use is not intended or documented, and because of the potential impact of the issue (we fear that most people won't use a new major version and the issue may not be resolved on many systems).

Commits

• 7caca94 v4.1.0
• 7bd34fb Update release notes
• 56fc676 test: run appveyor tests in Node 10
• ee30222 chore: disable sauce-labs
• 05e6293 chore: bump version of grunt-saucelabs
• 2db0d12 chore: add .idea and yarn-error.log to .gitignore
• edc6220 fix: disallow access to the constructor in templates to prevent RCE
• bacd473 chore: fix components/handlebars package.json and auto-update on release
• 27ac1ee Feat: Import TypeScript typings
• 78dd89c chore: Use node 10 to build handlebars
• Additional commits viewable in compare view

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