{"id":65433,"date":"2026-04-27T11:58:51","date_gmt":"2026-04-27T11:58:51","guid":{"rendered":"https:\/\/xeyecs.com\/xeyeacademy\/?p=65433"},"modified":"2026-08-25T12:41:13","modified_gmt":"2026-08-25T12:41:13","slug":"read-javascript-lines-like-pro-hackers-a-practical-guide","status":"publish","type":"post","link":"https:\/\/xeyecs.com\/xeyeacademy\/read-javascript-lines-like-pro-hackers-a-practical-guide\/","title":{"rendered":"Read JavaScript Lines Like Pro Hackers: A Practical Guide"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\">When approaching bug bounty programs or security assessments, one of the most overlooked areas is&nbsp;<strong>JavaScript files<\/strong>. These files often hide sensitive information, forgotten endpoints, or misconfigured tokens.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Reading JavaScript \u201clike a hacker\u201d means not just opening them in a browser, but systematically extracting, analyzing, and scanning them for secrets.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">In this guide, we\u2019ll walk through a workflow that uses command\u2011line tools to uncover hidden treasures inside JS files. Each command is explained in detail, and filenames are slightly altered to keep the workflow unique.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Step 1: Collect JavaScript Endpoints<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">cat urls_list.txt | subjs | sort -u > collected_js.txt<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>What it does<\/strong>:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>cat urls_list.txt \u2192 reads a file containing HTTP endpoints.<\/li>\n\n\n\n<li>subjs \u2192 extracts JavaScript file references from those endpoints.<\/li>\n\n\n\n<li>sort -u \u2192 sorts them uniquely, removing duplicates.<\/li>\n\n\n\n<li>Output \u2192 collected_js.txt now contains a clean list of JS files.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">This is your&nbsp;<strong>starting point<\/strong>: a curated list of JavaScript files linked to the target application.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Join&nbsp;<\/strong><a href=\"https:\/\/academy.xeyecs.com\/\" target=\"_blank\" rel=\"noreferrer noopener\">XEye Academy<\/a><strong>&nbsp;today and master penetration testing skills to become a certified cybersecurity expert.<\/strong><\/h3>\n\n\n\n<h2 class=\"wp-block-heading\">Step 2: Deep Crawl for Hidden JS<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">cat urls_list.txt | subjs | sort -u | katana -jc | grep -Ei &#8220;\\.js(\\?|$)&#8221; > deep_scan_js.txt<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>What it does<\/strong>:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>katana -jc \u2192 crawls deeper into the site, following JavaScript references.<\/li>\n\n\n\n<li>grep -Ei &#8220;\\.js(\\?|$)&#8221; \u2192 filters only .js files, even if they have query strings.<\/li>\n\n\n\n<li>Output \u2192 deep_scan_js.txt contains JS files discovered beyond the surface.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">This step ensures you don\u2019t miss&nbsp;<strong>deeply nested scripts<\/strong>&nbsp;that aren\u2019t obvious in the initial crawl.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Step 3: Secret Hunting in Hidden Files<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">while read link; do SecretFinder -i &#8220;$link&#8221; -o cli; done &lt; hidden_js.txt &gt; secrets_output.txt<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>What it does<\/strong>:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Loops through each URL in hidden_js.txt.<\/li>\n\n\n\n<li>Runs SecretFinder to detect API keys, tokens, or credentials.<\/li>\n\n\n\n<li>Outputs results into secrets_output.txt.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">This is where the&nbsp;<strong>real hacking mindset<\/strong>&nbsp;kicks in \u2014 scanning for sensitive strings that developers may have left behind.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Step 4: Grep for Common Secrets<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">grep -r -E &#8216;aws_access_key|aws_secret_key|api_key|passwd|pwd|firebase|swagger|password|.env|ssh_key|oauth_token&#8217; collected_js.txt<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>What it does<\/strong>:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Searches recursively for keywords that often indicate secrets.<\/li>\n\n\n\n<li>Targets AWS keys, Firebase configs, .env references, and OAuth tokens.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">This is a&nbsp;<strong>quick win technique<\/strong>: many times, developers accidentally hardcode credentials in JS files.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Step 5: Automated Scanning with Nuclei<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">nuclei -l collected_js.txt -tags js,secrets,exposure,token -o js_scan_results.txt<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>What it does<\/strong>:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Uses nuclei templates to scan JavaScript files for exposures.<\/li>\n\n\n\n<li>Tags focus on secrets, tokens, and misconfigurations.<\/li>\n\n\n\n<li>Results saved in js_scan_results.txt.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">This step automates vulnerability detection, combining your manual hunting with structured scans.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Join&nbsp;<\/strong><a href=\"https:\/\/academy.xeyecs.com\/\" target=\"_blank\" rel=\"noreferrer noopener\">XEye Academy<\/a><strong>&nbsp;today and master penetration testing skills to become a certified cybersecurity expert.<\/strong><\/h3>\n\n\n\n<h2 class=\"wp-block-heading\">Step 6: Alternative Quick Extraction<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">cat urls_list.txt | subjs | grep -Ei &#8220;\\.js(\\?|$)&#8221; | sort -u > quick_js.txt<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>What it does<\/strong>:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>A faster variation of Step 1.<\/li>\n\n\n\n<li>Directly extracts JS files without deep crawling.<\/li>\n\n\n\n<li>Useful when you want a\u00a0<strong>lightweight scan<\/strong>.<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">Step 7: Expanding with Wayback Machine URLs<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">waybackurls targetsite.com | grep &#8220;\\.js&#8221; | sort -u > archived_js.txt<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>What it does<\/strong>:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>waybackurls pulls historical URLs from the Wayback Machine.<\/li>\n\n\n\n<li>grep &#8220;\\.js&#8221; filters only JavaScript files.<\/li>\n\n\n\n<li>sort -u ensures uniqueness.<\/li>\n\n\n\n<li>Output \u2192 archived_js.txt contains JS files that may no longer be live but still reveal sensitive code.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">This is powerful because&nbsp;<strong>old JS files often contain forgotten API keys or endpoints<\/strong>&nbsp;that developers thought were gone.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Step 8: Using gau for Mass Enumeration<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">gau targetsite.com | grep &#8220;\\.js&#8221; | sort -u > gau_js.txt<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>What it does<\/strong>:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>gau (GetAllURLs) collects URLs from multiple sources (Wayback, Common Crawl, etc.).<\/li>\n\n\n\n<li>Filters .js files.<\/li>\n\n\n\n<li>Output \u2192 gau_js.txt gives you a broad set of JavaScript references.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">This complements waybackurls by pulling from&nbsp;<strong>different archives and feeds<\/strong>.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Step 9: Validating Endpoints with httpx<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">cat gau_js.txt | httpx -mc 200 -silent > live_js.txt<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>What it does<\/strong>:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>httpx checks which JS URLs are still live.<\/li>\n\n\n\n<li>-mc 200 ensures only HTTP 200 OK responses are kept.<\/li>\n\n\n\n<li>Output \u2192 live_js.txt is a verified list of accessible JS files.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">This step saves time by&nbsp;<strong>removing dead links<\/strong>&nbsp;before deeper analysis.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Step 10: Extracting Endpoints from JS<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">grep -Eo &#8216;(https?:\/\/[^&#8221;]+)&#8217; live_js.txt | sort -u > endpoints.txt<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>What it does<\/strong>:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Uses regex to extract URLs inside JS files.<\/li>\n\n\n\n<li>Collects API endpoints, hidden paths, or third\u2011party integrations.<\/li>\n\n\n\n<li>Output \u2192 endpoints.txt becomes a roadmap of potential attack surfaces.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">This is where you start&nbsp;<strong>pivoting from JS analysis to API testing.<\/strong><\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Step 11: Searching for Sensitive Configurations<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">grep -i -E &#8216;config|token|auth|secret|key|firebase&#8217; live_js.txt > config_hits.txt<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>What it does<\/strong>:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Targets keywords that often indicate sensitive configurations.<\/li>\n\n\n\n<li>Output \u2192 config_hits.txt highlights suspicious lines worth manual review.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">This is a&nbsp;<strong>quick filter<\/strong>&nbsp;to catch misconfigured integrations.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Step 12: Combining with Nuclei Templates<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">nuclei -l endpoints.txt -tags exposure,api,token -o endpoint_scan.txt<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>What it does<\/strong>:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Runs Nuclei against discovered endpoints.<\/li>\n\n\n\n<li>Focuses on exposure and token leaks.<\/li>\n\n\n\n<li>Output \u2192 endpoint_scan.txt provides structured vulnerability findings.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">This bridges the gap between&nbsp;<strong>manual discovery and automated testing<\/strong>.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Join&nbsp;<\/strong><a href=\"https:\/\/academy.xeyecs.com\/\" target=\"_blank\" rel=\"noreferrer noopener\">XEye Academy<\/a><strong>&nbsp;today and master penetration testing skills to become a certified cybersecurity expert.<\/strong><\/h3>\n\n\n\n<h2 class=\"wp-block-heading\">Step 13: Bonus \u2014 Extracting Comments from JS<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">grep -E &#8220;\/\/|\/\\*&#8221; live_js.txt > comments.txt<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>What it does<\/strong>:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Extracts developer comments inside JS files.<\/li>\n\n\n\n<li>Comments often reveal&nbsp;<strong>internal notes, TODOs, or deprecated endpoints<\/strong>.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Sometimes the most valuable intel comes from what developers casually leave behind.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Conclusion and Best Practices<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">By now, you\u2019ve seen how a hacker\u2011style workflow for reading JavaScript files can uncover hidden secrets, forgotten endpoints, and misconfigured tokens. The commands we walked through from subjs and katana to gau, httpx, and nuclei form a layered approach that combines&nbsp;<strong>manual discovery<\/strong>&nbsp;with&nbsp;<strong>automated scanning<\/strong>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">But tools alone don\u2019t make you effective. Here are some best practices to keep in mind:<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">1. Diversify Your Sources<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Don\u2019t rely only on live JS files.<\/li>\n\n\n\n<li>Use&nbsp;<strong>archived sources<\/strong>&nbsp;(waybackurls, gau) to find forgotten scripts.<\/li>\n\n\n\n<li>Validate with httpx to avoid wasting time on dead links.<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">2. Always Verify Findings<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>A regex hit doesn\u2019t mean a real secret.<\/li>\n\n\n\n<li>Cross\u2011check suspicious strings with context before reporting.<\/li>\n\n\n\n<li>Example: An api_key string might be a placeholder, not a live credential.<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">3. Respect Scope and Compliance<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Only test within authorized scope.<\/li>\n\n\n\n<li>Avoid scanning unrelated domains or third\u2011party scripts unless explicitly allowed.<\/li>\n\n\n\n<li>This keeps your work professional and audit\u2011ready.<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">4. Document Everything<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Save outputs (collected_js.txt, deep_scan_js.txt, endpoint_scan.txt).<\/li>\n\n\n\n<li>Screenshots and logs help clients understand your findings.<\/li>\n\n\n\n<li>Documentation also supports compliance frameworks like&nbsp;<strong>ISO 27001<\/strong>.<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">5. Think Like a Developer<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Look at comments (grep -E &#8220;\/\/|\/\\*&#8221;) for hints.<\/li>\n\n\n\n<li>Developers often leave TODOs or notes that point to hidden functionality.<\/li>\n\n\n\n<li>This mindset helps you anticipate where secrets might be buried.<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">6. Automate, But Don\u2019t Blindly Trust Automation<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Tools like nuclei are powerful, but they can miss context.<\/li>\n\n\n\n<li>Manual review of JS files often reveals subtle issues automation skips.<\/li>\n\n\n\n<li>Balance speed with depth.<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">Final Thoughts<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Reading JavaScript like a hacker isn\u2019t about memorizing commands, it\u2019s about building a&nbsp;<strong>workflow<\/strong>&nbsp;that uncovers what others overlook. By chaining together tools (subjs, katana, gau, httpx, SecretFinder, nuclei), you create a pipeline that transforms raw URLs into actionable intelligence.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">If you\u2019re doing any of bug bounty hunting, penetration testing, or compliance audits, this approach ensures you don\u2019t miss the hidden gems inside JS files. And remember:&nbsp;<strong>every JS file is a potential map to the backend,<\/strong>&nbsp;treat it with the same curiosity and rigor as you would any exposed API.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n","protected":false},"excerpt":{"rendered":"<p>When approaching bug bounty programs or security assessments, one of the most overlooked areas is&nbsp;JavaScript files. These files often hide sensitive information, forgotten endpoints, or misconfigured tokens. Reading JavaScript \u201clike a hacker\u201d means not just opening them in a browser, but systematically extracting, analyzing, and scanning them for secrets. In this guide, we\u2019ll walk through<a href=\"https:\/\/xeyecs.com\/xeyeacademy\/read-javascript-lines-like-pro-hackers-a-practical-guide\/\" class=\"more-link\"><span class=\"screen-reader-text\">Read JavaScript Lines Like Pro Hackers: A Practical Guide<\/span><\/a><\/p>\n","protected":false},"author":3,"featured_media":65434,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[332],"tags":[323,313,347],"class_list":["post-65433","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-tools-skills-development","tag-ethical-hacking","tag-penetration-testing","tag-website-hacking"],"_links":{"self":[{"href":"https:\/\/xeyecs.com\/xeyeacademy\/wp-json\/wp\/v2\/posts\/65433","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/xeyecs.com\/xeyeacademy\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/xeyecs.com\/xeyeacademy\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/xeyecs.com\/xeyeacademy\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/xeyecs.com\/xeyeacademy\/wp-json\/wp\/v2\/comments?post=65433"}],"version-history":[{"count":3,"href":"https:\/\/xeyecs.com\/xeyeacademy\/wp-json\/wp\/v2\/posts\/65433\/revisions"}],"predecessor-version":[{"id":66065,"href":"https:\/\/xeyecs.com\/xeyeacademy\/wp-json\/wp\/v2\/posts\/65433\/revisions\/66065"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/xeyecs.com\/xeyeacademy\/wp-json\/wp\/v2\/media\/65434"}],"wp:attachment":[{"href":"https:\/\/xeyecs.com\/xeyeacademy\/wp-json\/wp\/v2\/media?parent=65433"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/xeyecs.com\/xeyeacademy\/wp-json\/wp\/v2\/categories?post=65433"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/xeyecs.com\/xeyeacademy\/wp-json\/wp\/v2\/tags?post=65433"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}