CVE-2018-25061: rgb2hex vulnerable to inefficient regular expression complexity

The vulnerability stems from inefficient regex patterns in the color parsing logic. The pre-patch regex used \d+ (unbounded digits) and optional groups with overlapping match possibilities, creating exponential time complexity for certain inputs. The commit 9e0c385 explicitly addresses this by: 1) Adding (.*?) to prevent greedy matching attacks, 2) Limiting RGB components to \d{1,3}, 3) Constraining alpha values to [01]??.([0-9]{0,3}), and 4) Adjusting capture group indices. Both index.js and rgb2hex.js contained identical vulnerable regex patterns prior to patching, making their rgb2hex functions the attack surface.