Critical advisory for Elo

Advisory overview

Elo is a purely functional expression language for no-code tools. Prior to 1.0.1, plain Elo strings supplied to defaultFormats.elo.parse(), bin/elo, or elo-lang.org/try can use .constructor.constructor to reach JavaScript Function because the member_access handler in src/transform.ts does not reject meta-properties, src/compilers/javascript.ts emits the surviving property directly, and src/parser.ts accepts constructor as an ordinary identifier. The resulting generated JavaScript executes attacker-selected code in the host runtime. This permits browser script execution and session compromise on the auto-running playground and arbitrary Node.js code execution on library, CI, or DevOps hosts. This plain-string path is distinct from the programmatic AST-object injection issue. This issue is fixed in version 1.0.1.

Related references

• https://github.com/enspirit/elo/commit/2136da1f64eec8ebf99890d3100be9394534b842
• https://github.com/enspirit/elo/commit/d2a89a8db76a244eb740687524a7e8529b7554b5
• https://github.com/enspirit/elo/security/advisories/GHSA-33r5-xmm8-v6x5