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BurpExtenderAPI - java.lang.NullPointerException: Cannot invoke "burp.ehv.a(burp.ikb)" because "<parameter1>" is null

Daniel | Last updated: Aug 20, 2021 01:41PM UTC

Hello, I'm developing a burpsuite extension and I stumbled upon a problem with MessageEditorTab rendering. I have a basic plugin : BurpExtender.java - https://pastebin.com/xAZewdZT SimplePluginMessageEditorTab.java - https://pastebin.com/VFkZBnde That I test on Burp Suite Professional v2021.8.1 And I receive following stack trace each time I switch the editor entry in Issue Activity or Http proxy history section. https://pastebin.com/LePvzDLV PoC: https://drive.google.com/file/d/11NcZ75eX_hsnQJ3JwrevndGqebiBgs08/view?usp=sharing I'm using burp-extender-api 2.2 , yet the same behaviour can be observed with 1.7.22. Also I noticed that the some of the plugins available in the BApp Store (i.e JSON Web Tokens, JSON Web Token Attacker) suffers from the same issue, once I realised it I decided to write this post.

Uthman, PortSwigger Agent | Last updated: Aug 20, 2021 02:51PM UTC

Hi Daniel, You have set the interfaces to 'null' in line 11 and 12 of BurpExtender.java. That likely explains why this is not working as you would expect. For other extensions, if they have set some logic to define when the extension tab is displayed (using the isEnabled() function) then you will only see the extension tab UI when you meet certain conditions e.g. JQ (https://portswigger.net/bappstore/c0d90a42c99848588d3df017cca717b5) expects a JSON response It looks like you haven't defined any logic for the extension tab to do anything either? You may want to check out the example here to help you get started: - https://github.com/PortSwigger/example-custom-editor-tab

Daniel | Last updated: Aug 24, 2021 09:20AM UTC

Hello Uthman, The interfaces are being set at lines 20, 30. Therefore the issue must be caused by something else. I have checked the example, and it returns exactly the same error.

Uthman, PortSwigger Agent | Last updated: Aug 24, 2021 02:49PM UTC

Hi Daniel, Apologies, I misread that. I have managed to replicate this using JWT. I will ask our development team for some input and get back to you.

Uthman, PortSwigger Agent | Last updated: Aug 26, 2021 02:31PM UTC

Hi Daniel, Our development team has fixed this issue! We will update this thread when the next release is out. Thanks for reporting this and apologies for the confusion.

Daniel | Last updated: Aug 31, 2021 09:11AM UTC

Hi Uthman, Great to hear that! Looking forward for the new release. No problem :)

Liam, PortSwigger Agent | Last updated: Nov 02, 2021 12:33PM UTC

This issue should now be resolved. Please let us know if you need any further assistance.

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