LiquidJS is a Shopify / GitHub Pages compatible template engine in pure JavaScript. Prior to version 10.25.1, the replace_first filter in LiquidJS uses JavaScript's String.prototype.replace() which interprets $& as a back reference to the matched substring. The filter only charges memoryLimit for the input string length, not the amplified output. An attacker can achieve exponential memory amplification (up to 625,000:1) while staying within the memoryLimit budget, leading to denial of service. Version 10.25.1 patches the issue.