Impact

Our library allows strings to be parsed as functions and stored as a specialized component, JsonFunctionValue. To do this, Javascript's eval function was used to execute strings that begin with "function" as Javascript. This was an oversight that unfortunately allows arbitrary code to be executed if it exists as a value within the JSON structure being displayed. Given that this component may often be used to display data from arbitrary, untrusted sources, this is extremely dangerous.

One important note is that users who have defined a custom onSubmitValueParser callback prop on the JsonTree component should be unaffected. This vulnerability exists in the default onSubmitValueParser prop which calls parse.

Patches

We have decided on a two-pronged approach to patching this vulnerability:

1. Create a patch update that adds a workaround which is not enabled by default to preserve backwards-compatibility
2. On the next major update, we will enable this workaround by default

The workaround we have decided on is adding a prop to JsonTree called allowFunctionEvaluation. This prop will be set to true in v2.2.2, so you can upgrade without fear of losing backwards-compatibility.

We have also implemented additional security measures as we know many people may not read the details of this vulnerability, and we want to do the best we can to keep you protected. In v2.2.2, we switched from using eval to using Function to construct anonymous functions. This is better than eval for the following reasons:

• Arbitrary code should not be able to execute immediately, since the Function constructor explicitly only creates anonymous functions
• Functions are created without local closures, so they only have access to the global scope

This change has brought a slight potential for breaking backwards-compatibility if users for some reason were relying on side-effects of our usage of eval, but that is beyond intended behavior, so we have decided to go ahead with this change and consider it a non-breaking change.

Workarounds

As mentioned above, there are a few scenarios you must consider:

If you use:

• Version <2.2.2, you must upgrade as soon as possible.
• Version ^2.2.2, you must explicitly set JsonTree's allowFunctionEvaluation prop to false to fully mitigate this vulnerability.
• Version >=3.0.0, allowFunctionEvaluation is already set to false by default, so no further steps are necessary.

References

None.

For more information

If you have any questions or comments about this advisory:

• Open an issue in the GitHub repo