How web trackers exploit password managers

Martin Brinkmann
Dec 31, 2017

Most web browsers come with a built-in password manager, a basic tool to save login data to a database and fill out forms and/or sign in to sites automatically using the information that is in the database.

Users who want more functionality rely on third-party password managers like LastPass, KeePass or Dashlane. These password managers add functionality, and may install as browser extensions or desktop programs.

Research from Princeton's Center for Information Technology Policy suggest that newly discovered web trackers exploit password managers to track users.

The tracking scripts exploit a weakness in password managers. What happens is the following according to the researchers:

  1. A user visits a website, registers an account, and saves the data in the password manager.
  2. The tracking script runs on third-party sites. When a user visits the site, login forms are injected in the site invisibly.
  3. The browser's password manager will fill out the data if a matching site is found in the password manager.
  4. The script detects the username, hashes it, and sends it to third-party servers to track the user.

The following graphic representation visualizes the workflow.

password manager web tracker exploit

The researchers analyzed two different scripts designed to exploit password managers to get identifiable information about users. The two scripts, AdThink and OnAudience, inject invisible login forms in web pages to retrieve username data that is returned by the browser's password manager.

The script computes hashes and sends these hashes to third-party servers. The hash is used to track users across sites without the use of cookies or other forms of user tracking.

User tracking is one of the holy grails of online advertising. Companies use the data to create user profiles that record user interests based on a number of factors, for example based on the sites visited -- Sports, Entertainment, Politics, Science -- or from where a user connects to the Internet.

The scripts that the researchers analyzed focus on the username. Nothing is keeping other scripts from pulling password data as well however, something that malicious scripts have tried already in the past.

The researchers analyzed 50,000 websites, and found no traces of password dumping on any of them. They did find the tracking scripts on 1,100 of the top 1 million Alexa websites however.

The following scripts are used:

  • AdThink:
  • OnAudience:


opt-out tracking

The Adthink script contains very detailed categories for personal, financial, physical traits, as well as intents, interests and demographics.

The researchers describe the functionality of the script in the following way:

  1. The script reads the email address and sends MD5, SHA1 and SHA256 hashes to
  2. Another request sends the MD5 hash of the email address to the data broker Acxiom (

Internet users can check the status of tracking and opt out of the collecting of data on this page.


The OnAudience script is "most commonly present on Polish websites".

  1. The script computes the MD5 hash of email addresses, and also other browser data commonly used for fingerprinting (MIME types, plugins, screen dimensions, language, timezone information, user agent string, OS and CPU information).
  2. Another hash is generated based on the data.

Protection against login form web tracking

Users can install content blockers to block requests to the domains mentioned above. The EasyPrivacy list does that already, but it is easy enough to add the URLs to the blacklist manually.

Another defense is the disabling of login data auto-filling. Firefox users can set the preference about:config?filter=signon.autofillForms to false to disable autofilling.

Closing Words

Is the advertisement publishing industry shoveling its own grave? Invasive tracking scripts are yet another reason for users to install ad and content blockers in web browsers.

Yes, this site has ads as well. I wish there was another option to run an independent site, or a company that would offer native advertisement solutions that run only on the server a site runs on, and does not require third-party connections or use tracking.

You can support us through Patreon, PayPal, or by leaving a comment / spreading the word on the Internet.

How web trackers exploit password managers
Article Name
How web trackers exploit password managers
Research from Princeton's Center for Information Technology Policy suggest that newly discovered web trackers exploit password managers to track users.
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  1. ilev said on August 4, 2012 at 7:53 pm

    Doesn’t Windows 8 know that www. or http:// are passe ?

    1. Martin Brinkmann said on August 4, 2012 at 7:57 pm

      Well it is a bit difficulty to distinguish between domains and files for instance.

    2. Leonidas Burton said on September 4, 2023 at 4:51 am

      I know a service made by google that is similar to Google bookmarks.

  2. VioletMoon said on August 16, 2023 at 5:26 pm

    @Ashwin–Thankful you delighted my comment; who knows how many “gamers” would have disagreed!

  3. Karl said on August 17, 2023 at 10:36 pm


    The comments section under this very article (3 comments) is identical to the comments section found under the following article:

    Not sure what the issue is, but have seen this issue under some other articles recently but did not report it back then.

  4. Anonymous said on August 25, 2023 at 11:44 am

    Omg a badge!!!
    Some tangible reward lmao.

    It sucks that redditors are going to love the fuck out of it too.

  5. Scroogled said on August 25, 2023 at 10:57 pm

    With the cloud, there is no such thing as unlimited storage or privacy. Stop relying on these tech scums. Purchase your own hardware and develop your own solutions.

    1. lollmaoeven said on August 27, 2023 at 6:24 am

      This is a certified reddit cringe moment. Hilarious how the article’s author tries to dress it up like it’s anything more than a png for doing the reddit corporation’s moderation work for free (or for bribes from companies and political groups)

  6. El Duderino said on August 25, 2023 at 11:14 pm

    Almost al unlmited services have a real limit.

    And this comment is written on the dropbox article from August 25, 2023.

  7. John G. said on August 26, 2023 at 1:29 am

    First comment > @ilev said on August 4, 2012 at 7:53 pm

    For the God’s sake, fix the comments soon please! :[

  8. Kalmly said on August 26, 2023 at 4:42 pm

    Yes. Please. Fix the comments.

  9. Kim Schmidt said on September 3, 2023 at 3:42 pm

    With Google Chrome, it’s only been 1,500 for some time now.

    Anyone who wants to force me in such a way into buying something that I can get elsewhere for free will certainly never see a single dime from my side. I don’t even know how stupid their marketing department is to impose these limits on users instead of offering a valuable product to the paying faction. But they don’t. Even if you pay, you get something that is also available for free elsewhere.

    The algorithm has also become less and less savvy in terms of e.g. English/German translations. It used to be that the bot could sort of sense what you were trying to say and put it into different colloquialisms, which was even fun because it was like, “I know what you’re trying to say here, how about…” Now it’s in parts too stupid to translate the simplest sentences correctly, and the suggestions it makes are at times as moronic as those made by Google Translations.

    If this is a deep-learning AI that learns from users’ translations and the phrases they choose most often – which, by the way, is a valuable, moneys worthwhile contribution of every free user to this project: They invest their time and texts, thereby providing the necessary data for the AI to do the thing as nicely as they brag about it in the first place – alas, the more unprofessional users discovered the translator, the worse the language of this deep-learning bot has become, the greater the aggregate of linguistically illiterate users has become, and the worse the language of this deep-learning bot has become, as it now learns the drivel of every Tom, Dick and Harry out there, which is why I now get their Mickey Mouse language as suggestions: the inane language of people who can barely spell the alphabet, it seems.

    And as a thank you for our time and effort in helping them and their AI learn, they’ve lowered the limit from what was once 5,000 to now 1,500…? A big “fuck off” from here for that! Not a brass farthing from me for this attitude and behaviour, not in a hundred years.

  10. Anonymous said on September 28, 2023 at 8:19 am

    When will you put an end to the mess in the comments?

  11. RIP said on September 28, 2023 at 9:36 am

    Ghacks comments have been broken for too long. What article did you see this comment on? Reply below. If we get to 20 different articles we should all stop using the site in protest.

    I posted this on [] so please reply if you see it on a different article.

    1. RIP said on September 28, 2023 at 11:01 am

      Comment redirected me to [] which seems to be the ‘real’ article it is attached to

  12. RIP said on September 28, 2023 at 10:48 am

    Comment redirected me to [] which seems to be the ‘real’ article it is attached to

  13. Mystique said on September 28, 2023 at 12:13 pm

    Article Title: Reddit enforces user activity tracking on site to push advertising revenue
    Article URL:

    No surprises here. This is just the beginning really. I cannot see a valid reason as to why anyone would continue to use the platform anymore when there are enough alternatives fill that void.

  14. justputthispostanywhere said on September 29, 2023 at 3:59 am

    I’m not sure if there is a point in commenting given that comments seem to appear under random posts now, but I’ll try… this comment is for

    My temporary “solution”, if you can call it that, is to use a VPN (Mullvad in my case) to sign up for and access Reddit via a European connection. I’m doing that with pretty much everything now, at least until the rest of the world catches up with GDPR. I don’t think GDPR is a magical privacy solution but it’s at least a first step.

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