Closes the medium-severity dependabot alert on canvas/package-lock.json.
Upstream advisory GHSA-qx2v-qp2m-jg93: "PostCSS has XSS via Unescaped
</style> in its CSS Stringify Output" — fixed in 8.5.10. We pull
8.5.12 since it's already published in the ^8.5.10 line.
package.json's caret range bumps from ^8.4.0 to ^8.5.12 — wider floor
prevents a future install from re-pinning below the safe version. The
8.x major-line constraint is preserved, so no breaking-change risk.
Verification: full canvas vitest suite passes (1148/1148 across
78 files).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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