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Based in San Francisco, California, cside develops a client-side security platform designed to protect websites from browser-based attacks, third-party script vulnerabilities, and digital fraud. The venture-backed company operates a freemium business model and currently processes over 10 million web scripts daily across 70 distinct vulnerability attributes. The software provides script proxying, artificial intelligence-driven threat detection, and web supply chain visibility for enterprise customers operating in the financial services, healthcare, and retail sectors. The organization has secured financial backing from prominent technology executives, including former Google product leader and Vercel Chief Product Officer Kathy Korevec, alongside former Vercel Director of Product Management Edward Thomson. In August 2025, the company expanded its platform capabilities to detect artificial intelligence agents and prevent digital fraud, while simultaneously receiving multiple industry awards for its client-side protection and software performance.
cside has raised $9.7M across 3 funding rounds.
cside has raised $9.7M in total across 3 funding rounds.
cside has raised $9.7M in total across 3 funding rounds.
cside's investors include iNovia Capital, Mantis VC, Redpoint Ventures, Zain Rizavi, Scheinman Angel Fund, Scribble Ventures, Uncork Capital, Haley Daiber, Kevin Weil, Ron Pragides, 20VC, Accel.
cside has raised $9.7M across 3 funding rounds. Most recently, it raised $6.0M Seed in September 2024.
| Date | Round | Lead Investors | Other Investors | Status |
|---|---|---|---|---|
| Sep 1, 2024 | $6M Seed | — | Inovia Capital, Mantis VC, Redpoint Ventures, Zain Rizavi, Scheinman Angel Fund, Scribble Ventures, Uncork Capital, Haley Daiber, Kevin Weil, RON Pragides | Announced |
| May 16, 2024 | $1.7M Pre Seed | Scribble Ventures | — | Announced |
| May 1, 2024 | $2M Seed | — | 20VC, Accel, Benhamou Global Ventures, DNX Ventures, Exponent Founders Capital, Fusion Fund, Inovia Capital, LEGO Ventures, Mantis VC, Mohr Davidow Ventures, NOT Boring Capital, Otherwise Fund, Partech Ventures, Pelion Venture Partners, Redpoint Ventures, Zain Rizavi, Ridge Ventures, Scheinman Angel Fund, Scribble Ventures, TQ Ventures, Uncork Capital, Annelies Gamble, Ariel Maislos, Chris Cooper, Jeremy CAI, Karim Atiyeh, Kevin Weil, Lior Shiff, Mario Gabriele, Mario Götze, Riccardo Zacconi, RON Pragides, Scott Belsky, Sohail Prasad, Yair Weinberger | Announced |
cside (Client-side Development, Inc., aka c/side) is a cybersecurity company specializing in client-side protection for web applications, focusing on monitoring, securing, and optimizing vulnerable third-party JavaScript scripts in browsers.[3][5][6] It builds a lightweight proxy-based platform that detects and blocks malicious behaviors like formjacking, digital skimming, OAuth abuse, and data exfiltration in real time, serving eCommerce, finance, online retail, and web-dependent businesses facing rising browser-side threats.[3][5] The solution provides session-by-session visibility, risk classification, PCI DSS 4.0-compliant dashboards, and human-readable LLM-summarized script behaviors, solving the "browser blind spot" where traditional server-side tools lack visibility.[3][5][6]
With recent accolades including Cyber Defense Magazine’s Global InfoSec Award and SourceForge’s 2025 Top Performer, cside demonstrates strong growth momentum amid escalating attacks on over 72,000 compromised sites, as detailed in its 2025 Threat Report.[5]
cside was founded by Simon Wijckmans, its CEO, who identified the growing vulnerabilities from uncontrolled third-party scripts, OAuth abuse, and malicious browser behaviors that evade perimeter defenses.[5][6] Emerging from the shift in cyber threats to client-side execution—particularly dynamic third-party JavaScript loading different code per user session—cside launched to address this gap where website owners and users remain unaware of breaches managed by external parties.[6]
Early traction includes design partners for product testing, industry awards in 2025, and customer growth, with plans for a seed round to expand sales and hiring while iterating on its hybrid proxy architecture.[5][6]
cside rides the trend of perimeter shifts to client-side attacks, where third-party scripts and supply-chain exploits (e.g., via WordPress plugins, mobile campaigns) execute in browsers beyond server visibility.[3][5] Timing is critical amid 2025's escalation in OAuth hijacking and 72,000+ compromised sites, as traditional tools fail against dynamic, session-specific threats.[5]
Market forces like PCI DSS 4.0 mandates for script monitoring favor cside, enabling compliance for eCommerce and finance while influencing the ecosystem by setting standards for browser-side telemetry and proxy controls, pushing vendors toward full-session inspection over partial sampling.[3][5]
cside is poised to expand from third-party script security into broader client-side features, leveraging its seed raise for product iteration, sales channels, and hiring to onboard more users.[6] Trends like rising OAuth exploits, AI-enhanced detections, and regulatory pressures will shape its path, potentially evolving it into a full client-side security stack leader as browser threats dominate.
This positions cside as an essential shield in a web ecosystem where attackers increasingly target the user's browser, directly addressing the vulnerabilities that make NetSuite-like optimizations look tame by comparison.[1][3]
