ImageMagick is free and open-source software used for editing and manipulating digital images. ImageMagick versions lower than 14.8.2 include insecure functions: SeekBlob(), which permits advancing the stream offset beyond the current end without increasing capacity, and WriteBlob(), which then expands by quantum + length (amortized) instead of offset + length, and copies to data + offset. When offset ≫ extent, the copy targets memory beyond the allocation, producing a deterministic heap write on 64-bit builds. No 2⁶⁴ arithmetic wrap, external delegates, or policy settings are required. This is fixed in version 14.8.2.