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| Package Name | Ecosystem | Vulnerable Versions | First Patched Version |
|---|---|---|---|
| @prompty/core | npm | <= 0.1.4 | 0.1.5 |
| @prompty/core | npm | >= 2.0.0-alpha.1, <= 2.0.0-beta.4 | 2.0.0-beta.5 |
Miggo AIRoot Cause AnalysisThe vulnerability exists in the NunjucksRenderer.render function within @prompty/core. The function directly rendered Nunjucks templates without sanitizing the input data or restricting the execution environment. This allowed for Server-Side Template Injection (SSTI), enabling an attacker to execute arbitrary JavaScript code by accessing and manipulating object prototypes through crafted template syntax. The provided patch addresses this by introducing several security controls:
sanitizeInputs function recursively cleans the data passed to the template, removing any properties that are not own-properties and preventing prototype traversal.safeMemberLookup function is injected into the Nunjucks runtime to explicitly block access to sensitive properties like __proto__, constructor, and prototype.safeCallWrap function is used to completely disable the ability to call functions from within the template.The render method was modified to use a new renderSafely function, which orchestrates these security measures before rendering the template. The vulnerable function is NunjucksRenderer.render as it was the entry point for the untrusted data into the template engine.
NunjucksRenderer.renderruntime/typescript/packages/core/src/renderers/nunjucks.ts