An UPSERT discovered by OSSFuzz results in a corrupt database file:

CREATE TABLE t1(
  a INT,
  b INT,
  c INT UNIQUE,
  PRIMARY KEY(a,b)
) WITHOUT ROWID;
INSERT INTO t1(a,b) VALUES(json(3),4),(1,2) ON CONFLICT(a,b) DO NOTHING;
PRAGMA integrity_check;

The corruption is a missing entry from the unique index and is easily fixed using REINDEX. Nevertheless, this should not be happening.