with sequoia being released with base64 0.21 support, I will start preparing updates for the crates below (at least those maintained by the Rust team - coordinating with team members as necessary, of course).
I haven't decided yet whether uploading to experimental is the way to go, or whether straight to unstable post-bookworm makes more sense. I'll update this bug report accordingly. Versions of rust-base64 in unstable: librust-base64-dev 0.13.0-1 Versions of rdeps of rust-base64 in unstable, that also exist in testing: librust-alacritty-terminal-dev 0.17.0-1 depends on librust-base64-0.13+default-dev, librust-cargo-dev 0.66.0-1 depends on librust-base64-0.13+default-dev, librust-cookie-dev 0.16.0-1 depends on librust-base64-0.13+default-dev, librust-fernet-dev 0.2.0+really0.1.4-2 depends on librust-base64-0.13+default-dev, librust-grep-printer-dev 0.1.6-1 depends on librust-base64-0.13+default-dev, librust-jsonwebtoken-dev 8.2.0-1+b1 depends on librust-base64-0.13+default-dev, librust-oauth2-dev 4.3.0-1+b1 depends on librust-base64-0.13+default-dev, librust-pem-dev 1.0.2-1 depends on librust-base64-0.13+default-dev, librust-plist-dev 1.3.1-1 depends on librust-base64-0.13+default-dev, librust-postgres-protocol-dev 0.6.4-1+b1 depends on librust-base64-0.13+default-dev, librust-reqwest-dev 0.11.13-1 depends on librust-base64-0.13+default-dev, librust-ron-dev 0.7.1-1 depends on librust-base64-0.13+default-dev, librust-ruma-common-dev 0.10.5-2 depends on librust-base64-0.13+default-dev, librust-rust-argon2-dev 1.0.0-2 depends on librust-base64-0.13+default-dev, librust-rustls-pemfile-dev 1.0.0-1+b1 depends on librust-base64-0.13+default-dev, librust-sequoia-autocrypt-dev 0.24.0-1 depends on librust-base64+default-dev (>= 0.12-~~), librust-sequoia-net-dev 0.25.0-2 depends on librust-base64+default-dev (>= 0.12-~~), librust-sequoia-openpgp-dev 1.12.0-2 depends on librust-base64-0.13+default-dev | librust-base64-0.12+default-dev, librust-sniffglue-dev 0.15.0-3+b2 depends on librust-base64-0.13+default-dev, librust-totp-rs-dev 3.0.1-2 depends on librust-base64-0.13+default-dev, librust-transmission-client-dev 0.1.3-2 depends on librust-base64-0.13+default-dev, librust-ureq-dev 2.6.2-3 depends on librust-base64-0.13+default-dev, Source packages in unstable whose autopkgtests are triggered by rust-base64: rust-base64ct 1.5.1-1 triggered by librust-base64-dev=0.13.0-1 rust-native-tls 0.2.11-1 triggered by librust-base64-dev=0.13.0-1 rust-psa-crypto 0.9.2-2 triggered by librust-base64-dev=0.13.0-1 rust-rustls 0.20.8-4 triggered by librust-base64-dev=0.13.0-1 rust-ttf-parser 0.15.2-1 triggered by librust-base64-dev=0.13.0-1 rust-webpki 0.22.0-1 triggered by librust-base64-dev=0.13.0-1