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In the competitive rental market of San Francisco, every advantage counts. For one developer, that advantage came in an unexpected form: a laundry app that, through a series of technical explorations, revealed not just optimal washing times but also a significant security vulnerability affecting potentially thousands of residents.

The journey began during a routine apartment hunt. "After weeks of getting beat out for every apartment I applied to, I finally found one where I wasn't applicant #11," the developer explained in a detailed account of their experience. The apartment lacked an in-unit washer and dryer, but featured a basement laundry room with a dedicated mobile app called Wash Connect.

The app, available only on Android and iOS, allowed residents to check machine availability remotely. This sparked an idea: could the developer analyze laundry patterns to avoid waiting? What followed was a deep dive into mobile application reverse engineering that uncovered far more than just optimal washing times.

The Technical Dive

With no web app available, the developer turned to traffic interception techniques. "I went down the rabbit hole of intercepting traffic from an Android app and ended up with a rooted virtual device and HTTP Toolkit," they recounted. After creating a burner account and identifying the APIs being called, they employed AI assistance to build a scraper that ran on a Linode server.

The scraper operated without incident for several days, but a closer examination of the code revealed a startling discovery: the API lacked authentication. "I thought to myself, can I analyze laundry habits for the entire country?" the developer wondered upon realizing the unrestricted access to the data.

Geocoding the Data

With access to nationwide data seemingly possible, the developer faced a new challenge: mapping laundry rooms to their physical addresses. Two key pieces of information proved crucial:

  1. The room name field contained the first line of the room's address
  2. The first two digits of a location's identifier represented the state code

"Pasting these two parts into Google usually identified the full address," the developer explained. They automated this process using the Google Maps Geocoding API, though acknowledged the method wasn't perfect.

Security Discovery and Response

After a week of operation, the scraper's IP was blocked, likely due to the high volume of traffic. The developer scaled back to focus only on San Francisco locations and ran the scraper throughout October.

During this period, they discovered and reported a significant security issue: the lack of authentication on the API. "I contacted the Wash team to report this, and they told me they were already aware and had intentionally decided to keep the data publicly accessible," the developer noted.

This decision raises questions about the balance between convenience and security in smart building applications. While public access to laundry availability might seem harmless, the same approach could expose far more sensitive data in other contexts.

San Francisco Laundry Patterns Revealed

The month-long data collection yielded fascinating insights into urban laundry behavior:

  • Wash Connect operates 451 laundry rooms in San Francisco with 2,095 washers and 2,023 dryers
  • Most locations have fewer than 10 machines, likely serving condos and smaller apartments
  • While most rooms maintain a 1:1 washer-to-dryer ratio, dryer usage typically runs higher due to longer cycle times
  • Time of day matters far more than day of week, with peak usage occurring on Sunday at 11 a.m.

These findings demonstrate how seemingly mundane data can reveal patterns about urban living when properly collected and analyzed. The developer's work shows how accessible APIs can provide valuable insights—but also how they can create security risks if not properly secured.

As smart home and building technologies proliferate, the Wash Connect case serves as a cautionary tale. The convenience of open APIs comes with responsibility, and what seems like harmless data today could be part of a larger security picture tomorrow. For developers and security professionals, the lesson is clear: even the most seemingly innocuous endpoints deserve proper authentication and access controls.