Versions 0.2.0 to 0.3.0 of ark-r1cs-std did not enforce any constraints in the FieldVar::mul_by_inverse method, allowing a malicious prover to produce an unsound proof that passes all verifier checks.
This method was used primarily in scalar multiplication for <code>short_weierstrass::ProjectiveVar</code>.
This bug was fixed in commit 47ddbaa, and was released as part of version 0.3.1 on crates.io.
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