## Description
Adds `VIPS_BLOCK_UNTRUSTED=1` to `.env.example`. This tells libvips to
only use its trusted, well-tested loaders when Active Storage generates
image variants, hardening image processing against untrusted uploads.
The setting requires libvips >= 8.13 and is silently ignored on older
versions.
Related to https://linear.app/chatwoot/issue/INF-92
## Type of change
- [x] Bug fix (non-breaking change which fixes an issue)
## How Has This Been Tested?
Verified locally that thumbnail/variant generation for the common raster
formats (JPEG, PNG, GIF, WebP, TIFF, HEIC) is unaffected with the flag
enabled.
## Checklist:
- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
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