security: diskcache CVE-2025-69872 (pickle deserialization) — remove obsolete pin

[bjoernbethge]

Alert

Dependabot alert #29

• Severity: medium
• CVE: CVE-2025-69872
• Package: diskcache <= 5.6.3
• Issue: DiskCache uses Python pickle for serialization by default. An attacker with write access to the cache directory can achieve arbitrary code execution when a victim application reads from the cache.
• Upstream fix: none available (latest release 5.6.3 is still vulnerable).

Our exposure

Zero. diskcache is not imported anywhere in src/ or examples/, and uv tree --invert shows marimo-flow itself as the only consumer:

diskcache v5.6.3
└── marimo-flow v0.2.0

The pin was added in commit 6c01457 as a security floor for a transitive dependency that has since gone away (probably dropped when we slimmed dependencies for 0.2.0).

Fix

Remove the line from pyproject.toml:

-    "diskcache>=5.6.3",

Then uv lock && uv sync. diskcache drops out of the resolution tree, the Dependabot alert auto-closes.

Alternatives (if we ever need diskcache back)

• Track upstream: https://github.com/grantjenks/python-diskcache/issues — no patched release as of 2026-04-20.
• If it reappears as a transitive, set the cache directory to a non-world-writable path and avoid unpickling untrusted cache.