Introduction
This is one of the first articles in a series of articles based on the hackerone bug bounty program by grammarly.
In this article we are going to get introduced to data poisoning attacks and will discuss label flipping with a working example on the grammarly APIs itself.
Model Poisoning
Model poisoning is a type of adversarial attack that targets machine learning models, particularly during their training phase. The goal of model poisoning is to subtly alter the model's behavior by introducing malicious data or manipulating the training process, causing the model to make incorrect predictions or behave in a way that benefits the attacker.
Label Flipping
This attack involves marking correct input with incorrect label and incorrect input with correct label so that the model starts giving wrong predictions
In the context of grammarly we will try to investigate the grammarly web app and APIs that power spelling correctness feature.
The investigation
- Ruling out server side AI model support
- Checked for activity in the network tab
- Could only see
logV2,eventsandauthorizationrequests in the network logs
logV2
POST /logv2 HTTP/2
Host: f-log-editor.grammarly.io
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:109.0) Gecko/20100101 Firefox/117.0
Accept: */*
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate, br
Referer: https://app.grammarly.com/
Content-Type: application/json
Content-Length: 2914
Origin: https://app.grammarly.com
Connection: keep-alive
Sec-Fetch-Dest: empty
Sec-Fetch-Mode: cors
Sec-Fetch-Site: cross-site
TE: trailers
This is probably a logging API sending user and user-agent related info on every page reload
events
curl 'https://gnar.grammarly.com/events' -X POST -H 'User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:109.0) Gecko/20100101 Firefox/117.0' -H 'Accept: */*' -H 'Accept-Language: en-US,en;q=0.5' -H 'Accept-Encoding: gzip, deflate, br' -H 'Referer: https://app.grammarly.com/' -H 'Content-Type: application/json' -H 'Origin: https://app.grammarly.com' -H 'Connection: keep-alive' -H 'Cookie: grauth=AABN_y5k8nO1QVQ7lyDTKrp_68vQR2HUQFVp5r3NklXGkfJRIn2CJM1Hqn7WxAU1bhjxbJNgtpF_xPCi; csrf-token=AABN/9Bb12L12hlkibY1S8ONAetDOcsjuYIc5g; gnar_containerId=xjaj96uqklmu0902; _gcl_au=1.1.2013238534.1725196671; _ga_CBK9K2ZWWE=GS1.1.1725200925.2.0.1725200925.60.0.0; _ga=GA1.1.469893869.1725196671; _pin_unauth=dWlkPU4yTTRORFEzWVRrdFpXTmtNaTAwTkRKakxUazVaVGt0TkRFeVlUSTFZams1TVRrMQ; __podscribe_grammarly_referrer=https://www.google.com/; __podscribe_grammarly_landing_url=https://www.grammarly.com/ai-writing-assistant; __podscribe_did=pscrb_f542134c-de91-49e8-99de-dca7bab0e0cb; _tq_id.TV-7281365481-1.3988=69840ec454ed06bc.1725196672.0.1725200923..; _clck=1o62qwl%7C2%7Cfow%7C0%7C1705; _fbp=fb.1.1725196673331.19073762163984477; funnelType=free; tdi=tmwup2itzfdtt5czk; last_authn_event=666f04d3-a2ac-4b8a-b152-ff82465ee922; gac=AABN_0pbfOxu1yQOL6aAyc1jL4ELkaY4_eC9XZbBF3nANLbuz9K9n_TbuLizWGC1YPd60rEy2PrW7SJrVozu2REsn5a11gxzmUTEUuMiPCFpc3Yu; isGrammarlyUser=true; experiment_groups=gb_analytics_mvp_phase_one_30_day_enabled|auto_complete_correct_safari_enabled|extension_assistant_bundles_all_consumers_enabled|officeaddin_ue_exp3_enabled|fsrw_in_assistant_all_consumers_enabled|extension_new_rich_text_fields_enabled|safari_migration_inline_disabled_enabled|officeaddin_upgrade_state_exp1_enabled1|officeaddin_outcomes_ui_exp5_enabled1|premium_ungating_renewal_notification_enabled|kaza_security_hub_enabled|extension_assistant_all_consumers_enabled|quarantine_messages_enabled|small_hover_menus_existing_enabled|fsrw_in_assistant_all_enabled|emogenie_beta_enabled|gb_snippets_csv_upload_enabled|grammarly_web_ukraine_logo_dapi_enabled|extension_fluid_for_all_rollout_test_enabled|officeaddin_upgrade_state_exp2_enabled1|apply_formatting_all_enabled|gb_analytics_mvp_phase_one_enabled|wonderpass_enabled|extensionfrench rap songsfrench rap songs_assistant_experiment_all_enabled|apply_formatting_all_consumers_enabled|gdocs_for_all_safari_enabled|extension_assistant_all_enabled|safari_migration_backup_notif1_enabled|ipm_extension_release_test_1|auto_complete_correct_edge_enabled|snippets_in_ws_gate_enabled|extension_assistant_experiment_all_consumers_enabled|extension_assistant_bundles_all_enabled|safari_migration_popup_editor_disabled_enabled|officeaddin_proofit_exp3_enabled|safari_migration_inline_warning_enabled|gb_in_editor_free_Test1|gdocs_for_all_firefox_enabled|gdocs_new_mapping_enabled|officeaddin_muted_alerts_exp2_enabled1|officeaddin_perf_exp3_enabled|shared_workspaces_enabled; _rdt_uuid=1725196671125.3dfe8c32-2a63-4036-a141-50c3f417cb98; _uetvid=97301a70686411efbb3e2ddb14c6081b; _clsk=1yrnj8i%7C1725419260716%7C1%7C0%7Cz.clarity.ms%2Fcollect; redirect_location=eyJ0eXBlIjoiIiwibG9jYXRpb24iOiJodHRwczovL2FwcC5ncmFtbWFybHkuY29tL2Rkb2NzLzI1Njg3MjI3NDcifQ==; browser_info=FIREFOX:117:COMPUTER:SUPPORTED:FREEMIUM:LINUX:LINUX' -H 'Sec-Fetch-Dest: empty' -H 'Sec-Fetch-Mode: cors' -H 'Sec-Fetch-Site: same-site' -H 'TE: trailers' --data-raw '{"events":[{"action":"show","eventName":"editor/assistant-lens-show","object":"lens","objectId":"assistant","lens":"all-suggestions","pageId":"document","client":"editor","clientVersion":"1.5.43-6200+master","instanceId":"0RGsM5vY","batchId":5,"containerId":"xjaj96uqklmu0902","userId":"2460910660","isTest":false,"userAgent":"Mozilla/5.0 (X11; Linux x86_64; rv:109.0) Gecko/20100101 Firefox/117.0","screenWidth":1920,"screenHeight":1080,"containerWidth":612,"containerHeight":887,"devicePixelRatio":1}]}'
This API also reports the current UI filters and userAgent details but also sends server side cookies for communication with podscribe
No data gets transported on repeated reload of the web page
All of the above was written around 27 August 2024, it was the last time I changed my root user password.
I updated the links today to the hackerone website and grammarly hackerone project, maybe they will expire in the coming future but the thrill of making money while exploring the interconnected products and their architecture is something that brings a smile on my face this Engineer's Day :).
Happy Engineer's Day
K
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